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Community-Acquired Pneumonia (Clinical)

Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia is the infection of the lung parenchyma, resulting from the spread of pathogens and accompanied by the host inflammatory response. This condition is the most common infectious cause of death. Multiple organisms cause pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, including bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology (of which Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pneumoniae is the most common), viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology, and fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology. When pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia is acquired outside the hospital setting, it is classified as community-acquired pneumonia Community-Acquired Pneumonia Pneumonia in Children (CAP). Common symptoms include fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, chills Chills The sudden sensation of being cold. It may be accompanied by shivering. Fever, cough, chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea. Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests usually shows consolidation Consolidation Pulmonary Function Tests and/or infiltrates. Diagnosis can be made with clinical presentation and imaging, but in severe cases, microbiological testing (sputum Gram stain Gram stain Klebsiella and cultures, molecular testing) and routine blood tests are needed. Empiric treatment with antibiotics is recommended, with regimen depending on the setting, risk factors for multidrug resistant Multidrug resistant Resistant to at least 1 agent in > 3 antibiotic categories Pseudomonas organisms, and individual comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus. Identification Identification Defense Mechanisms of the causative pathogen helps narrow down the antibiotics. Preventive measures include vaccinations (pneumococcal and influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza) and smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases cessation.

Last updated: Mar 4, 2024

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Definition

Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia is the infection of the lung parenchyma.

Types of pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia

Classification based on the site where infection was acquired:[1,2,8]

  • Community-acquired pneumonia Community-Acquired Pneumonia Pneumonia in Children (CAP): pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia acquired outside the hospital setting
  • Hospital-acquired pneumonia Hospital-Acquired Pneumonia Pneumonia in Children (HAP):
    • Nosocomial pneumonia Nosocomial pneumonia Pneumonia in Children 
    • Lung infection Lung infection Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia acquired 48 hours after admission into the hospital (infection was not incubating at the time of admission)
    • Not associated with mechanical ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing
  • Ventilator-associated pneumonia Ventilator-Associated Pneumonia Multidrug-resistant Organisms and Nosocomial Infections: pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia acquired 48 hours after endotracheal intubation Intubation Peritonsillar Abscess 
  • Notable update in the classification regarding health care–associated pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (HCAP):[15] 
    • Retired term
    • Was defined as pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia in individuals who had healthcare exposure (e.g., hospitalized, resident in a long-term care facility) 
    • Encompassed a large group labeled as high risk for multi-drug resistant organisms (MDRO), and this led to significant use of broad-spectrum Broad-Spectrum Fluoroquinolones antibiotics
    • Further studies showed that MDROs were not common in this population.[16]  
    • The concept of HCAP is NOT used in the most recent US guidelines:[13]
      • To reduce use of unnecessary antibiotics
      • To decrease antibiotic resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing

Classification by etiology:[17,18]

  • Aspiration pneumonia Aspiration pneumonia A type of lung inflammation resulting from the aspiration of food, liquid, or gastric contents into the upper respiratory tract. Pneumonia: infectious process developing due to the entry of gastric or oropharyngeal contents (containing pathogenic bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology) into the lower airways
  • “Typical” pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia:
    • Lung infection Lung infection Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia generally affecting the lobes (lobar) and/or surrounding tissues of the airways (bronchial)
    • Has the usual presentation of pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia: fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, chills Chills The sudden sensation of being cold. It may be accompanied by shivering. Fever, cough
    • Caused by the typical bacterial organisms, such as Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pneumoniae and Haemophilus influenzae Haemophilus Influenzae A species of Haemophilus found on the mucous membranes of humans and a variety of animals. The species is further divided into biotypes I through viii. Haemophilus
  • Atypical pneumonia Atypical pneumonia Mycoplasma:
    • Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia caused by atypical organisms ( Mycoplasma pneumoniae Mycoplasma pneumoniae Short filamentous organism of the genus mycoplasma, which binds firmly to the cells of the respiratory epithelium. It is one of the etiologic agents of non-viral primary atypical pneumonia in man. Mycoplasma, Chlamydia pneumoniae Chlamydia pneumoniae A species of chlamydophila that causes acute respiratory infection, especially atypical pneumonia, in humans, horses, and koalas. Chlamydia, Chlamydia psittaci Chlamydia psittaci A genus of chlamydophila infecting primarily birds. It contains eight known serovars, some of which infect more than one type of host, including humans. Chlamydia, Coxiella burnetii Coxiella burnetii A species of gram-negative bacteria that grows preferentially in the vacuoles of the host cell. It is the etiological agent of q fever. Coxiella/Q Fever)
    • Organisms involved are not detected by standard microbiological methods.
    • Additionally, milder symptoms are noted compared to the pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia due to S. pneumoniae.

Epidemiology[8]

General:

  • Most common cause of death due to infection in the United States
  • Higher mortality Mortality All deaths reported in a given population. Measures of Health Status rates in developing countries
  • Leading cause of death in children under 5 years of age worldwide
  • More common in winter Winter Pityriasis Rosea and in colder climates
  • Higher incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency and mortality Mortality All deaths reported in a given population. Measures of Health Status rate in advanced age

CAP:

  • 80% of CAP cases are treated as outpatients.
  • Most common cause of death from infection in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship > 65 years
  • Almost 1 out of 5 CAP inpatients are rehospitalized within 1 month.
  • CAP mortality Mortality All deaths reported in a given population. Measures of Health Status rate is highest at age extremes.

Etiology and Pathophysiology

Etiology[2,6,20]

  • Bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology (typical):
    • Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pneumoniae (most common bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology)
    • Haemophilus influenzae Haemophilus Influenzae A species of Haemophilus found on the mucous membranes of humans and a variety of animals. The species is further divided into biotypes I through viii. Haemophilus (2nd most common)
    • Moraxella catarrhalis Moraxella catarrhalis Gram-negative aerobic cocci of low virulence that colonize the nasopharynx and occasionally cause meningitis; bacteremia; empyema; pericarditis; and pneumonia. Moraxella
    • Staphylococcus aureus Staphylococcus aureus Potentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications. Brain Abscess
    • Group A streptococci
    • Aerobic gram-negative bacteria gram-negative bacteria Bacteria which lose crystal violet stain but are stained pink when treated by gram’s method. Bacteriology (e.g., Pseudomonas aeruginosa Pseudomonas aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas Enterobacteriaceae Enterobacteriaceae A family of gram-negative, facultatively anaerobic, rod-shaped bacteria that do not form endospores. Its organisms are distributed worldwide with some being saprophytes and others being plant and animal parasites. Many species are of considerable economic importance due to their pathogenic effects on agriculture and livestock. Cephalosporins such as Klebsiella Klebsiella Klebsiella are encapsulated gram-negative, lactose-fermenting bacilli. They form pink colonies on MacConkey agar due to lactose fermentation. The main virulence factor is a polysaccharide capsule. Klebsiella pneumoniae is the most important pathogenic species. Klebsiella spp. or Escherichia coli Escherichia coli The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. Escherichia coli)
    • Microaerophilic Microaerophilic Helicobacter bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology and anaerobes Anaerobes Lincosamides (noted in aspiration)
  • Atypical bacteria Atypical Bacteria Tetracyclines:
    • Mycoplasma pneumoniae Mycoplasma pneumoniae Short filamentous organism of the genus mycoplasma, which binds firmly to the cells of the respiratory epithelium. It is one of the etiologic agents of non-viral primary atypical pneumonia in man. Mycoplasma (most common cause of atypical pneumonia Atypical pneumonia Mycoplasma)
    • Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis spp. (transmitted via aerosols Aerosols Colloids with a gaseous dispersing phase and either liquid (fog) or solid (smoke) dispersed phase; used in fumigation or in inhalation therapy; may contain propellant agents. Coxiella/Q Fever)
    • Chlamydia pneumoniae Chlamydia pneumoniae A species of chlamydophila that causes acute respiratory infection, especially atypical pneumonia, in humans, horses, and koalas. Chlamydia
    • Chlamydia psittaci Chlamydia psittaci A genus of chlamydophila infecting primarily birds. It contains eight known serovars, some of which infect more than one type of host, including humans. Chlamydia
    • Coxiella burnetii Coxiella burnetii A species of gram-negative bacteria that grows preferentially in the vacuoles of the host cell. It is the etiological agent of q fever. Coxiella/Q Fever
  • Respiratory viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology:
    • Influenza A Influenza A Antivirals for Influenza and B viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology
    • Severe acute respiratory syndrome coronavirus Severe acute respiratory syndrome coronavirus A viral disorder characterized by high fever, dry cough, shortness of breath (dyspnea) or breathing difficulties, and atypical pneumonia. A virus in the genus Coronavirus is the suspected agent. Coronavirus 2 (SARS-CoV-2)
    • Other coronaviruses (e.g., CoV-229E, CoV-NL63)
    • Respiratory syncytial virus Respiratory Syncytial Virus Respiratory syncytial virus (RSV) is an enveloped, single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae and the genus Orthopneumovirus. Two subtypes (A and B) are present in outbreaks, but type A causes more severe disease. Respiratory syncytial virus causes infections of the lungs and respiratory tract. Respiratory Syncytial Virus
    • Adenoviruses
    • Rhinoviruses
    • Parainfluenza viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology
    • Human bocaviruses
    • Human metapneumovirus Human Metapneumovirus Acute Bronchiolitis
Table: Common pathogens detected based on the site of care[2,14]
Outpatient Non-ICU Inpatient ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus
  • S. pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • M. pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • Respiratory viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology
  • S. pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • M. pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • H. influenzae H. influenzae A species of Haemophilus found on the mucous membranes of humans and a variety of animals. The species is further divided into biotypes I through VIII. Haemophilus
  • Respiratory viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology
  • Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis spp.
  • S. pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • Staphylococcus aureus Staphylococcus aureus Potentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications. Brain Abscess
  • Gram-negative bacilli Bacilli Shigella
  • H. influenzae H. influenzae A species of Haemophilus found on the mucous membranes of humans and a variety of animals. The species is further divided into biotypes I through VIII. Haemophilus
  • Respiratory viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology

Risk factors[1,2,8]

General:

  • Ages > 65 years and < 2 years
  • Immunosuppression
  • Chronic conditions (especially cardiopulmonary diseases, asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma)
  • Reduced gag/cough reflex
  • Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
  • Institutionalization (e.g., hospital, nursing home)
  • Living in crowded conditions
  • Alcoholism Alcoholism A primary, chronic disease with genetic, psychosocial, and environmental factors influencing its development and manifestations. The disease is often progressive and fatal. It is characterized by impaired control over drinking, preoccupation with the drug alcohol, use of alcohol despite adverse consequences, and distortions in thinking, most notably denial. Each of these symptoms may be continuous or periodic. Wernicke Encephalopathy and Korsakoff Syndrome

Specific:

  • Common organisms and specific risk factors:
    • S. pneumoniae: dementia Dementia Major neurocognitive disorders (NCD), also known as dementia, are a group of diseases characterized by decline in a person’s memory and executive function. These disorders are progressive and persistent diseases that are the leading cause of disability among elderly people worldwide. Major Neurocognitive Disorders, seizure disorders, heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR), cerebrovascular disease, alcoholism Alcoholism A primary, chronic disease with genetic, psychosocial, and environmental factors influencing its development and manifestations. The disease is often progressive and fatal. It is characterized by impaired control over drinking, preoccupation with the drug alcohol, use of alcohol despite adverse consequences, and distortions in thinking, most notably denial. Each of these symptoms may be continuous or periodic. Wernicke Encephalopathy and Korsakoff Syndrome, smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD), HIV HIV Anti-HIV Drugs
    • Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis spp.: immunosuppression, diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus, malignancy Malignancy Hemothorax, HIV HIV Anti-HIV Drugs, smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, male sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria, and a recent hotel stay or ship cruise
    • H. influenzae H. influenzae A species of Haemophilus found on the mucous membranes of humans and a variety of animals. The species is further divided into biotypes I through VIII. Haemophilus: smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD)
    • K. pneumoniae: increased in those with aspiration risk, such as in alcohol abuse
  • Additional risk factors to consider:
    • Residence in, or travel to endemic areas with fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology:
    • History of specific exposures (in travel, occupation/hobby):
      • Histoplasma Histoplasma Histoplasmosis is an infection caused by Histoplasma capsulatum, a dimorphic fungus. The fungus exists as a mold at low temperatures and as yeast at high temperatures. H. capsulatum is the most common endemic fungal infection in the US and is most prevalent in the midwestern and central states along the Ohio and Mississippi River valleys. Histoplasma/Histoplasmosis spp. and bat or bird droppings
      • C. psittaci and birds
    • Travel in areas with outbreaks Outbreaks Sudden increase in the incidence of a disease. The concept includes epidemics and pandemics. Influenza Viruses/Influenza:
      • Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza (e.g., avian influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza H5N1 and H7N9)
      • SARS
      • Middle Eastern respiratory syndrome (MERS)
    • Bioterrorism Bioterrorism The use of biological agents in terrorism. This includes the malevolent use of bacteria; viruses; or other biological toxins against people, animals; or plants. Anthrax events:
      • Bacillus anthracis Bacillus anthracis A species of bacteria that causes anthrax in humans and animals. Anthrax ( anthrax Anthrax Anthrax is an infection caused by the bacterium Bacillus anthracis, which usually targets the skin, lungs, or intestines. Anthrax is a zoonotic disease and is usually transmitted to humans from animals or through animal products. Symptoms depend on which organ system is affected. Anthrax)
      • Yersinia pestis Yersinia pestis The plague is a bacterial infection caused by Yersinia pestis (Y. pestis), which primarily infects rodents. The disease is transmitted to humans via a flea bite. Inhalation of infectious droplets and handling infected animals or laboratory specimens are other means of transmission. The plague has 3 forms: bubonic (most common form), septicemic, and pneumonic. Yersinia pestis/Plague ( pneumonic plague Pneumonic Plague Yersinia pestis/Plague)
      • Coxiella burnetii Coxiella burnetii A species of gram-negative bacteria that grows preferentially in the vacuoles of the host cell. It is the etiological agent of q fever. Coxiella/Q Fever (Q fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever)
      • Francisella tularensis Francisella Tularensis Aminoglycosides (tularemia)
      • Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis spp
      • Hantavirus Hantavirus A genus of the family bunyaviridae causing hantavirus infections, first identified during the korean war. Infection is found primarily in rodents and humans. Transmission does not appear to involve arthropods. Hantaan virus is the type species. Bunyavirales and influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology
  • Risks for multidrug-resistant organisms (MDRO), methicillin-resistant Staphylococcus aureus Staphylococcus aureus Potentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications. Brain Abscess ( MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus) and Pseudomonas aeruginosa Pseudomonas aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas:
    • Less commonly found in CAP but should be considered in those with comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus and healthcare exposures
    • Seen more in HAP and VAP
    • Emphasis has been placed on determining the likelihood for these infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease due to the associated complications and the additional treatment needed.
    • Strong risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (see table):[1,8,16]
      • Prior MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus infection (strongest risk)
      • Known MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus colonization Colonization Bacteriology 
      • Gram-positive Gram-Positive Penicillins cocci Cocci Bacteriology in sputum
    • Strong risk factors for P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia:[1,6,8,16]
      • Prior Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas infection (strongest risk)
      • Known Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas colonization Colonization Bacteriology
      • Hospitalization Hospitalization The confinement of a patient in a hospital. Delirium with IV antibiotics in the past 3 months
      • Gram-negative rods in sputum
    • The 2019 American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) guidelines:[1]
      • Instead of broadly categorizing all who had been exposed through a health care system, the HCAP category was eliminated.
      • The focus now has been on identifying local etiologic data and validated risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus and P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas in deciding treatment.
Table: Risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus and P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas CAP
MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas
Strong risk factors
  • Prior MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus infection
  • Known MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus colonization Colonization Bacteriology
  • Hospitalization Hospitalization The confinement of a patient in a hospital. Delirium with IV antibiotics in the past 3 months
  • Gram-positive Gram-Positive Penicillins cocci Cocci Bacteriology in sputum
  • Prior Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas infection
  • Known Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas colonization Colonization Bacteriology
  • Hospitalization Hospitalization The confinement of a patient in a hospital. Delirium with IV antibiotics in the past 3 months
  • Gram-negative rods in sputum
Other considered factors that increase suspicion of infection
  • Recent hospitalization Hospitalization The confinement of a patient in a hospital. Delirium or antibiotic use (especially IV antibiotics)
  • Necrotizing pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • Empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia
  • Influenza-like illness
  • Immunosuppression
  • IV drug use
  • End-stage renal disease
  • Incarceration Incarceration Inguinal Canal: Anatomy and Hernias/crowded living situations
  • Contact sports
  • Men who have sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria with men
  • Recent hospital or long-term facility stay
  • Recent antibiotic use
  • Numerous COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) exacerbations treated with steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors and/or antibiotics
  • Structural lung disease ( cystic Cystic Fibrocystic Change fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, bronchiectasis Bronchiectasis Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Bronchiectasis)
  • Immunosuppression
MRSA: methicillin-resistant Staphylococcus aureus
CAP: community-acquired pneumonia
COPD: chronic obstructive pulmonary disease

Pathophysiology[2,8,19]

  • Main route:
    • Transmission commonly via respiratory droplets Droplets Varicella-Zoster Virus/Chickenpox (or aerosol) → organisms colonize the nasopharynx Nasopharynx The top portion of the pharynx situated posterior to the nose and superior to the soft palate. The nasopharynx is the posterior extension of the nasal cavities and has a respiratory function. Pharynx: Anatomy
    • Small-volume aspiration of pathogens such as bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology → access to, and proliferation in alveolar space → immune response through alveolar macrophages Alveolar macrophages Round, granular, mononuclear phagocytes found in the alveoli of the lungs. They ingest small inhaled particles resulting in degradation and presentation of the antigen to immunocompetent cells. Acute Respiratory Distress Syndrome (ARDS) → localized capillary leak and alveolar infiltration → symptoms and signs of pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
    • Respiratory defense mechanisms Defense mechanisms Defense mechanisms are normal subconscious means of resolving inner conflicts between an individual’s subjective moral sense and their thoughts, feelings, or actions. Defense mechanisms serve to protect the self from unpleasant feelings (anxiety, shame, and/or guilt) and are divided into pathologic, immature, mature, neurotic, and other types. Defense Mechanisms that must be overcome to cause parenchymal infection:
      • Nasal hair and turbinates Turbinates The scroll-like bony plates with curved margins on the lateral wall of the nasal cavity. Turbinates, also called nasal concha, increase the surface area of nasal cavity thus providing a mechanism for rapid warming and humidification of air as it passes to the lung. Nose Anatomy (External & Internal)
      • Gag and cough reflex
      • Tracheobronchial tree and its mucociliary lining
      • Alveolar macrophages Alveolar macrophages Round, granular, mononuclear phagocytes found in the alveoli of the lungs. They ingest small inhaled particles resulting in degradation and presentation of the antigen to immunocompetent cells. Acute Respiratory Distress Syndrome (ARDS)
  • Other routes:
    • Hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases (e.g., right heart endocarditis Endocarditis Endocarditis is an inflammatory disease involving the inner lining (endometrium) of the heart, most commonly affecting the cardiac valves. Both infectious and noninfectious etiologies lead to vegetations on the valve leaflets. Patients may present with nonspecific symptoms such as fever and fatigue. Endocarditis)
    • Contiguous spread (pleural or mediastinal infection)
  • Alternative pathogenesis: A defect in the normal defense mechanism Defense mechanism Unconscious process used by an individual or a group of individuals in order to cope with impulses, feelings or ideas which are not acceptable at their conscious level; various types include reaction formation, projection and self reversal. Psychotherapy of the airways facilitates overgrowth of the normal airway Airway ABCDE Assessment microbiota, causing pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia.
  • Typical pathologic phases for bacterial lobar pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia:[19]
    • Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema or congestion: increase in alveolar exudate Exudate Exudates are fluids, cells, or other cellular substances that are slowly discharged from blood vessels usually from inflamed tissues. Pleural Effusion containing the pathogenic organism
    • Red hepatization: predominant presence of erythrocytes Erythrocytes Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology with neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation, fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis and occasional bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology in the exudate Exudate Exudates are fluids, cells, or other cellular substances that are slowly discharged from blood vessels usually from inflamed tissues. Pleural Effusion, resembling the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy (“hepatization”)
    • Gray hepatization (successful control of infection): predominant presence of neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation and fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis as the RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology break down (↓ erythrocytes Erythrocytes Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology)
    • Resolution: predominant presence of macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation with the clearing of neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation and fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis

Clinical Presentation

Symptoms[2,21]

  • Respiratory:
    • Cough:
      • Productive (mucoid, purulent, or blood-tinged sputum)
      • Nonproductive (mostly with atypical pneumonia Atypical pneumonia Mycoplasma)
      • Gross hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis (seen in MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus)
    • Dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea (mild to severe)
    • Pleuritic chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
  • Nonspecific symptoms:
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Palpitations Palpitations Ebstein’s Anomaly
    • Chills Chills The sudden sensation of being cold. It may be accompanied by shivering. Fever
    • Night sweats Night sweats Tuberculosis
    • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia
    • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics and/or vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
    • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
    • Myalgias Myalgias Painful sensation in the muscles. Tick-borne Encephalitis Virus
    • Arthralgia Arthralgia Pain in the joint. Rheumatic Fever
  • Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia in the elderly may present with confusion.

Physical examination[2,21]

  • Tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children
  • Respiratory rate Respiratory rate The number of times an organism breathes with the lungs (respiration) per unit time, usually per minute. Pulmonary Examination and use of accessory muscles
  • Tactile fremitus Tactile Fremitus Pulmonary Examination and dull percussion Percussion Act of striking a part with short, sharp blows as an aid in diagnosing the condition beneath the sound obtained. Pulmonary Examination consolidation Consolidation Pulmonary Function Tests
  • Tactile fremitus Tactile Fremitus Pulmonary Examination and flat/dull percussion Percussion Act of striking a part with short, sharp blows as an aid in diagnosing the condition beneath the sound obtained. Pulmonary Examination pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion
  • Auscultation findings can include:
    • Crackles
    • Bronchial sounds in the periphery
    • Pleural friction rub
  • Severe cases may present with signs of septic shock Septic shock Sepsis associated with hypotension or hypoperfusion despite adequate fluid resuscitation. Perfusion abnormalities may include, but are not limited to lactic acidosis; oliguria; or acute alteration in mental status. Sepsis and Septic Shock and multiorgan failure.

Diagnosis

Initial diagnostic approach[2,3,21] 

The diagnosis is based on clinical findings (signs and symptoms) and imaging.

  • Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests:
    • Test of choice in most cases
    • For clinically suspected pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, obtain posteroanterior (PA) and lateral chest radiographs.
    • Findings may include:
      • Lobar consolidations
      • Interstitial infiltrates
      • Cavitations
      • Pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion
    • Findings may be absent if:
      • Early in the course of disease
      • Patient is dehydrated → consider re-imaging after rehydration Rehydration Dengue Virus
  • Chest CT:
    • Some patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship may require for evaluation of:
      • Suspected tumors
      • Foreign bodies
      • Cavitary lesions
    • Helpful when detection of inflammatory changes may not be apparent on X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests:
      • Inflammatory changes may not be evident in immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship.
      • Chronic lung disease (e.g., pulmonary fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, bronchiectasis Bronchiectasis Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Bronchiectasis) may obscure the visualization of infiltrates.
    • CT angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery may be used to rule out pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism as a cause of respiratory symptoms.

Determining the etiology[1,2,5,6,12,21–23]

Generally, in mild CAP being treated on an outpatient basis, microbiologic testing is not necessary except for SARS-CoV-2 and influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza (during influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza season). For inpatient management, several tests are obtained, depending on the severity, underlying illness, and epidemiologic exposures.

  • Sputum and blood cultures:
    • Not routinely obtained in the outpatient setting.
    • Recommended in the inpatient setting for the following:
      • Severe pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (especially if the patient is intubated)
      • Likely infection with MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus or Pseudomonas aeruginosa Pseudomonas aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas
      • Previously hospitalized and treated with parenteral antibiotics in the last 90 days
    • Obtaining these tests allows:
      • Identification Identification Defense Mechanisms of a resistant organism
      • Narrowing down of antibiotic use 
      • Appropriate antibiotic choice(s) when initial therapy fails
      • Determination of public health risk (e.g., Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis is reportable)
  • Test for influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza:
    • During influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza season, testing for influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza is recommended.
    • Includes:
      • Rapid influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza molecular assay ( influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza nucleic acid amplification Nucleic acid amplification Laboratory techniques that involve the in-vitro synthesis of many copies of DNA or RNA from one original template. Septic Arthritis test, which is preferred)
      • Rapid influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination test
    • Testing helps determine the need for antiviral Antiviral Antivirals for Hepatitis B therapy.
  • Test for SARS-CoV-2: 
    • Test in all with suspected CAP.[3]
    • In settings where resources are limited, testing priorities for SARS-CoV-2 include:
      • Critically ill individuals
      • Symptomatic healthcare workers/first responders
      • Symptomatic individuals who are immunosuppressed, are ≥ 65 years old, or have comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus
      • Symptomatic critical infrastructure workers, healthcare workers, or first responders
  • Pneumococcus and Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination:
    • Urinary antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination test for detection of Legionella pneumophila Legionella pneumophila A species of gram-negative, aerobic bacteria that is the causative agent of legionnaires’ disease. It has been isolated from numerous environmental sites as well as from human lung tissue, respiratory secretions, and blood. Legionella/Legionellosis or pneumococcus
    • Urine pneumococcal antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination: not routinely tested except in severe CAP[1,6]
    • Urine Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination is not routinely tested, but recommended in the following:
      • Severe CAP
      • Legionella Legionella Legionella is a facultative intracellular, gram-negative bacilli. Legionella does not grow on common culture media because it requires certain supplementation (cysteine and iron). Legionella pneumophila (L. pneumophila) accounts for the majority of human infections. Legionella/Legionellosis outbreak in the community or travel to an area affected by an outbreak
  • Other respiratory viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology:
    • Not recommended for outpatients
    • Testing should be considered in hospitalized individuals in the following circumstances:
      • Severe CAP
      • Immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
    • Viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology detected can vary depending on lab and test manufacturer, but may include:
      • Respiratory syncytial virus Respiratory Syncytial Virus Respiratory syncytial virus (RSV) is an enveloped, single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae and the genus Orthopneumovirus. Two subtypes (A and B) are present in outbreaks, but type A causes more severe disease. Respiratory syncytial virus causes infections of the lungs and respiratory tract. Respiratory Syncytial Virus ( RSV RSV Respiratory syncytial virus (RSV) is an enveloped, single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae and the genus Orthopneumovirus. Two subtypes (A and B) are present in outbreaks, but type A causes more severe disease. Respiratory syncytial virus causes infections of the lungs and respiratory tract. Respiratory Syncytial Virus)
      • Adenovirus Adenovirus Adenovirus (member of the family Adenoviridae) is a nonenveloped, double-stranded DNA virus. Adenovirus is transmitted in a variety of ways, and it can have various presentations based on the site of entry. Presentation can include febrile pharyngitis, conjunctivitis, acute respiratory disease, atypical pneumonia, and gastroenteritis. Adenovirus
      • Parainfluenza virus Parainfluenza virus Human parainfluenza viruses (HPIVs) are single-stranded, linear, negative-sense RNA viruses of the family Paramyxoviridae and the genus Paramyxovirus. Human parainfluenza viruses are the 2nd most common cause of lower respiratory disease in children, after the respiratory syncytial virus. Parainfluenza Virus
      • Rhinovirus Rhinovirus Rhinovirus is an acid-labile, positive-sense RNA virus of the Picornavirus family. The virus, which causes the common cold, is most often acquired through the airway via the inhalation of aerosols containing rhinovirus and fomites. Rhinovirus
      • Human metapneumovirus Human Metapneumovirus Acute Bronchiolitis
  • Rapid nasal PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) or culture for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus is obtained in:
    • Severe CAP
    • Those at risk for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus
    • Those with progressive deterioration
  • Other tests can be added depending on the indication:
    • Cavitary pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia → test for Nocardia Nocardia Nocardia is a branching, filamentous, gram-positive bacilli. It is partially acid fast due to the presence of mycolic acids in the cell wall. Nocardia is a ubiquitous soil organism that most commonly affects immunocompromised patients. Nocardia is transmitted via inhalation of aerosolized bacteria or less commonly, via direct contact with wounds. Nocardia/Nocardiosis, tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis, and other fungal organisms
    • Immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis → include tests for:
      • Pneumocystis jiroveci Pneumocystis jiroveci Pneumocystis jiroveci is a yeast-like fungus causing pneumocystis pneumonia (PCP) in immunocompromised patients. Pneumocystis pneumonia is spread through airborne transmission and classically affects patients with AIDS, functioning as an AIDS-defining illness. Patients may present with insidious onset of fever, chills, dry cough, chest pain, and shortness of breath. Pneumocystis jirovecii/Pneumocystis Pneumonia (PCP)
      • Fungal pathogens
      • Less common viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology
    • Exposure and travel → check for zoonotic pathogens
    • If bronchoscopy Bronchoscopy Endoscopic examination, therapy or surgery of the bronchi. Laryngomalacia and Tracheomalacia is pursued, additional multiplex molecular assays (that detect other viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology and bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology) are sent.

Additional laboratory tests[1–3,6,7,14,21,23]

Mostly obtained in the hospital setting to help assess severity of illness and other underlying disorders:

  • CBC:
    • Usually, leukocytosis Leukocytosis A transient increase in the number of leukocytes in a body fluid. West Nile Virus with a leftward shift
    • Leukopenia and thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia are associated with severe CAP.
  • Metabolic panel:
    • Newly ↑ BUN and creatinine indicate poorer prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas.
    • Abnormal liver function tests Liver function tests Liver function tests, also known as hepatic function panels, are one of the most commonly performed screening blood tests. Such tests are also used to detect, evaluate, and monitor acute and chronic liver diseases. Liver Function Tests are also noted in sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock.
  • Inflammatory markers:
    • CRP may help in screening Screening Preoperative Care, when combined with clinical signs and symptoms
    • In UK:
      • Antibiotic therapy is not recommended if CRP is < 20 mg/L (low risk for CAP)
      • Repeated in hospitalized patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship if unclear clinical progress (after 48–72 hours)
  • Arterial blood gas Arterial blood gas Respiratory Alkalosis:
    • Obtain in cases of respiratory distress or failure
    • pH pH The quantitative measurement of the acidity or basicity of a solution. Acid-Base Balance and/or low oxygen are findings noted in severe CAP.
  • Procalcitonin Procalcitonin Neutropenic Fever:
    • Some studies indicate that the level of procalcitonin Procalcitonin Neutropenic Fever can help distinguish viral from bacterial infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, but sensitivity varies greatly (38%–91%).
    • May have some prognostic value in deciding treatment setting
    • Empiric treatment for CAP is started regardless of the procalcitonin Procalcitonin Neutropenic Fever level.
  • Screen for HIV HIV Anti-HIV Drugs:
    • Consider if patient has risk factors and/or is unresponsive to standard therapy
    • Directs workup needed, especially for opportunistic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
    • Affects therapeutic management

Management

Recommendations may vary depending on practice location, regional epidemiology, and availability of drug therapy. The following is a summary derived largely from the ATS/IDSA guidelines. For detailed information, ATS/IDSA guidelines (US), UK guidelines, and European guidelines are available for review.

Risk assessment Risk assessment The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. Preoperative Care

In addition to clinical judgment Judgment The process of discovering or asserting an objective or intrinsic relation between two objects or concepts; a faculty or power that enables a person to make judgments; the process of bringing to light and asserting the implicit meaning of a concept; a critical evaluation of a person or situation. Psychiatric Assessment, a validated prediction tool is recommended to determine the severity of infection and need for hospitalization Hospitalization The confinement of a patient in a hospital. Delirium

Severity assessment on initial evaluation:Tools such as the  Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia Severity Index (PSI) and CURB-65 (Confusion, blood U rea ReA Reactive arthritis is a seronegative autoimmune spondyloarthropathy that occurs in response to a previous gastrointestinal (GI) or genitourinary (GU) infection. The disease manifests as asymmetric oligoarthritis (particularly of large joints in the lower extremities), enthesopathy, dactylitis, and/or sacroiliitis. Reactive Arthritis nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle, Respiratory rate, Blood pressure, and age ≥ 65 years) predict 30-day mortality Mortality All deaths reported in a given population. Measures of Health Status from the time of diagnosis. The choice of tool varies depending on the practice location.

  • Preferred tool: Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia Severity Index (PSI)[1,2,7,14] 
    • Calculator
    • Preferred by the ATS and IDSA
    • Classifies larger portion of those with CAP as low risk, allowing safe outpatient treatment 
    • Points are assigned based on different risk factors:
      • Demographics
      • Comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus
      • Physical examination findings
      • Laboratory tests (e.g., arterial pH pH The quantitative measurement of the acidity or basicity of a solution. Acid-Base Balance, blood urea Urea A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea Cycle nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle, serum sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia and glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance, hematocrit Hematocrit The volume of packed red blood cells in a blood specimen. The volume is measured by centrifugation in a tube with graduated markings, or with automated blood cell counters. It is an indicator of erythrocyte status in disease. For example, anemia shows a low value; polycythemia, a high value. Neonatal Polycythemia, partial pressure Partial pressure The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. Gas Exchange of oxygen) 
      • Imaging (e.g., pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion)
    • Total points are added and classified in to different risk classes (I–V), with higher points indicating higher mortality Mortality All deaths reported in a given population. Measures of Health Status rate:
      • Class I or II → sent home on oral antibiotics
      • Class III → may be sent home on oral antibiotics or admitted for short-term monitoring and antibiotic therapy based on home environment and follow-up
      • Class IV or V → hospitalized
  • Alternative tool: CURB-65[1,2,5–7,14]
    • Calculator:
      • Recommended by the European Society of Clinical Microbiology and Infectious Diseases and British Thoracic Society (BTS)
      • Less complex than PSI
    • One point for each of the following:
      • Confusion
      • Blood urea Urea A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea Cycle nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle ≥ 20 mg/dL
      • Respirations ≥ 30/min
      • Systolic blood pressure < 90 mm Hg or diastolic blood pressure < 60 mm Hg
      • Age ≥ 65 years
    • Points are added together, with higher points indicating higher mortality Mortality All deaths reported in a given population. Measures of Health Status rate:

Intensive care admission assessment (severe CAP):

  • ATS/IDSA criteria for defining severe CAP → presence of CAP and must meet major or minor criteria:[1,6,14]
    • ≥ 1 of the following (major criteria):
      • Septic shock Septic shock Sepsis associated with hypotension or hypoperfusion despite adequate fluid resuscitation. Perfusion abnormalities may include, but are not limited to lactic acidosis; oliguria; or acute alteration in mental status. Sepsis and Septic Shock or hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension requiring vasopressors Vasopressors Sepsis in Children
      • Respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure requiring mechanical ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing
    • ≥ 3 of the following (minor criteria):
      • Confusion
      • Respirations ≥ 30/min
      • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension requiring aggressive fluid management
      • Core temperature < 36 ℃
      • WBC < 4,000 cells/µL
      • Platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology < 100,000/µL
      • Blood urea Urea A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea Cycle nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle ≥ 20 mg/dL
      • Partial pressure Partial pressure The pressure that would be exerted by one component of a mixture of gases if it were present alone in a container. Gas Exchange of oxygen (PaO2)/fraction of inspired oxygen (FiO2) ≤ 250
      • Multilobar pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • SMART-COP criteria:[1,7,14]
    • Alternative prediction tool in determining those who would need vasopressor Vasopressor Acute Cholangitis and/or mechanical ventilatory support
    • Most patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship used in the study were > 50 years of age, so sensitivity is reduced when used in those < 50.
    • Elements:
      • Systolic blood pressure (low or < 90 mm Hg)
      • Multilobar pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
      • Albumin ( hypoalbuminemia Hypoalbuminemia A condition in which albumin level in blood (serum albumin) is below the normal range. Hypoalbuminemia may be due to decreased hepatic albumin synthesis, increased albumin catabolism, altered albumin distribution, or albumin loss through the urine (albuminuria). Nephrotic Syndrome in Children)
      • Respiratory rate (elevated)
      • Tachycardia
      • Confusion
      • Oxygenation (low)
      • pH (low arterial pH pH The quantitative measurement of the acidity or basicity of a solution. Acid-Base Balance)

Overview of treatment[1,2,4,6]

  • Majority of those diagnosed with CAP are treated empirically.
  • Differences in initial treatment are affected by severity of CAP and comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus.
  • Serum procalcitonin Procalcitonin Neutropenic Fever levels should not influence the decision to treat pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia with antibiotics.

Outpatient treatment

Antibiotic options for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship without comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus:[1,2,4,5,13] 

  • Amoxicillin Amoxicillin A broad-spectrum semisynthetic antibiotic similar to ampicillin except that its resistance to gastric acid permits higher serum levels with oral administration. Penicillins
  • Doxycycline
  • Azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides (or clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides) → use only if pneumococcal resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing to macrolides Macrolides Macrolides and ketolides are antibiotics that inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit and blocking transpeptidation. These antibiotics have a broad spectrum of antimicrobial activity but are best known for their coverage of atypical microorganisms. Macrolides and Ketolides is < 25% in the community

Antibiotic options for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus:[1,2,13]

  • Examples of comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus to consider:
    • Congestive heart disease
    • Chronic lung disease
    • Malignancy Malignancy Hemothorax
    • Cerebrovascular disease
    • Renal disease
    • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy disease
    • Asplenia Asplenia Asplenia is the absence of splenic tissue or function and can stem from several factors ranging from congenital to iatrogenic. There is a distinction between anatomic asplenia, which is due to the surgical removal of the spleen, and functional asplenia, which is due to a condition that leads to splenic atrophy, infarct, congestion, or infiltrative disease. Asplenia
    • Alcohol dependence
  • Combination therapy:
    • Typically includes 1 of these:
    • Plus 1 of the following:
      • Macrolide ( azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides or clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides)
      • Doxycycline
  • Monotherapy options:
    • Levofloxacin Levofloxacin The l-isomer of ofloxacin. Fluoroquinolones
    • Moxifloxacin Moxifloxacin A fluoroquinolone that acts as an inhibitor of DNA topoisomerase II and is used as a broad-spectrum antibacterial agent. Fluoroquinolones
    • Gemifloxacin Gemifloxacin A naphthyridine and fluoroquinolone derivative antibacterial agent and DNA topoisomerase II inhibitor that is used for the treatment of community-acquired pneumonia and acute bacterial infections associated with chronic bronchitis. Fluoroquinolones (not available in the U.S.)
Table: Outpatient therapy for community-acquired pneumonia Community-Acquired Pneumonia Pneumonia in Children[1]
Risk category Regimen Antibiotic options Typical dose (adult)
No comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus Monotherapy Amoxicillin Amoxicillin A broad-spectrum semisynthetic antibiotic similar to ampicillin except that its resistance to gastric acid permits higher serum levels with oral administration. Penicillins
  • US: 1 g 3 times daily
  • UK: 500 mg (or higher) 3 times daily[4]
Azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides
  • 500 mg on day 1
  • Then 250 mg daily
Clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides 500 mg twice daily
Doxycycline 100 mg twice daily
With comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus* Combination therapy ( beta-lactam Beta-Lactam Penicillins plus macrolide or doxycycline) Amoxicillin Amoxicillin A broad-spectrum semisynthetic antibiotic similar to ampicillin except that its resistance to gastric acid permits higher serum levels with oral administration. Penicillins–clavulanate Options include:
  • 500 mg/125 mg 3 times daily
  • 875 mg/125 mg twice daily
  • 2,000 mg/125 mg twice daily
Cefpodoxime 200 mg twice daily
Cefuroxime 500 mg twice daily
Azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides
  • 500 mg on day 1
  • Then 250 mg daily
Clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides 500 mg twice daily
Doxycycline 100 mg twice daily
Monotherapy Levofloxacin Levofloxacin The l-isomer of ofloxacin. Fluoroquinolones 750 mg daily
Moxifloxacin Moxifloxacin A fluoroquinolone that acts as an inhibitor of DNA topoisomerase II and is used as a broad-spectrum antibacterial agent. Fluoroquinolones 400 mg daily
Gemifloxacin Gemifloxacin A naphthyridine and fluoroquinolone derivative antibacterial agent and DNA topoisomerase II inhibitor that is used for the treatment of community-acquired pneumonia and acute bacterial infections associated with chronic bronchitis. Fluoroquinolones 320 mg daily
*Includes chronic heart, lung, liver, or renal disease; diabetes mellitus; alcohol dependence; malignancy; or asplenia

Inpatient treatment

Antibiotic options will depend on the severity of infection and presence of MDR organism risk factors.

Nonsevere CAP antibiotic options:

  • With no MDR risk factors:[1,2]
    • Combination therapy:
      • 1 of the following: ampicillin Ampicillin Semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic. Penicillins sulbactam Sulbactam A beta-lactamase inhibitor with very weak antibacterial action. The compound prevents antibiotic destruction of beta-lactam antibiotics by inhibiting beta-lactamases, thus extending their spectrum activity. Combinations of sulbactam with beta-lactam antibiotics have been used successfully for the therapy of infections caused by organisms resistant to the antibiotic alone. Cephalosporins, cefotaxime Cefotaxime Semisynthetic broad-spectrum cephalosporin. Cephalosporins, ceftriaxone Ceftriaxone A broad-spectrum cephalosporin antibiotic and cefotaxime derivative with a very long half-life and high penetrability to meninges, eyes and inner ears. Cephalosporins, or ceftaroline Ceftaroline Cephalosporins 
      • Plus 1 of the following: azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides, clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides, or doxycycline
    • Monotherapy options (respiratory fluoroquinolone):
  • With ≥ 2 risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus:[1,2]
    • Add empiric coverage to those with prior respiratory isolation of MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus or positive culture:
      • Vancomycin Vancomycin Antibacterial obtained from streptomyces orientalis. It is a glycopeptide related to ristocetin that inhibits bacterial cell wall assembly and is toxic to kidneys and the inner ear. Glycopeptides
      • Linezolid Linezolid An oxazolidinone and acetamide derived anti-bacterial agent and protein synthesis inhibitor that is used in the treatment of gram-positive bacterial infections of the skin and respiratory tract. Oxazolidinones
      • Note: daptomycin Daptomycin A cyclic lipopeptide antibiotic that inhibits gram-positive bacteria. Lipopeptides and Lipoglycopeptides is not effective for respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease → inhibited by pulmonary surfactant Surfactant Substances and drugs that lower the surface tension of the mucoid layer lining the pulmonary alveoli. Acute Respiratory Distress Syndrome (ARDS)
    • For those with prior hospitalization Hospitalization The confinement of a patient in a hospital. Delirium with parenteral antibiotics, first obtain culture → add coverage if positive
    • Cultures are required to determine the need to continue therapy.
  • With risk factors for P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas:[1,2]
    • Use an antipneumococcal and antipseudomonal β-lactam in those with prior isolation of Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas or positive culture:
      • Piperacillin Piperacillin Semisynthetic, broad-spectrum, ampicillin derived ureidopenicillin antibiotic proposed for pseudomonas infections. It is also used in combination with other antibiotics. Penicillins tazobactam Tazobactam A penicillanic acid and sulfone derivative and potent beta-lactamase inhibitor that enhances the activity of other anti-bacterial agents against beta-lactamase producing bacteria. Cephalosporins 
      • Cefepime Cefepime A fourth-generation cephalosporin antibacterial agent that is used in the treatment of infections, including those of the abdomen, urinary tract, respiratory tract, and skin. It is effective against pseudomonas aeruginosa and may also be used in the empiric treatment of febrile neutropenia. Cephalosporins 
      • Ceftazidime Ceftazidime Semisynthetic, broad-spectrum antibacterial derived from cephaloridine and used especially for pseudomonas and other gram-negative infections in debilitated patients. Cephalosporins 
      • Imipenem Imipenem Semisynthetic thienamycin that has a wide spectrum of antibacterial activity against gram-negative and gram-positive aerobic and anaerobic bacteria, including many multiresistant strains. It is stable to beta-lactamases. Clinical studies have demonstrated high efficacy in the treatment of infections of various body systems. Its effectiveness is enhanced when it is administered in combination with cilastatin, a renal dipeptidase inhibitor. Carbapenems and Aztreonam 
      • Meropenem Meropenem A thienamycin derivative antibacterial agent that is more stable to renal dehydropeptidase I than imipenem, but does not need to be given with an enzyme inhibitor such as cilastatin. It is used in the treatment of bacterial infections, including infections in immunocompromised patients. Carbapenems and Aztreonam
      • Alternative: aztreonam Aztreonam The carbapenems and aztreonam are both members of the bactericidal beta-lactam family of antibiotics (similar to penicillins). They work by preventing bacteria from producing their cell wall, ultimately leading to bacterial cell death. Carbapenems and Aztreonam
    • For those with prior hospitalization Hospitalization The confinement of a patient in a hospital. Delirium with parenteral antibiotics, obtain culture first → add coverage if positive
    • Cultures are required to determine the need to continue therapy.
Table: Inpatient therapy for nonsevere community-acquired pneumonia Community-Acquired Pneumonia Pneumonia in Children[1]
Risk category Regimen Antibiotic options Typical dose (adult)
No risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus or P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas Combination therapy (antipneumococcal β-lactam plus a macrolide or doxycycline) Ampicillin Ampicillin Semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic. Penicillins sulbactam Sulbactam A beta-lactamase inhibitor with very weak antibacterial action. The compound prevents antibiotic destruction of beta-lactam antibiotics by inhibiting beta-lactamases, thus extending their spectrum activity. Combinations of sulbactam with beta-lactam antibiotics have been used successfully for the therapy of infections caused by organisms resistant to the antibiotic alone. Cephalosporins 1.5–3 g every 6 hours
Cefotaxime Cefotaxime Semisynthetic broad-spectrum cephalosporin. Cephalosporins 1–2 g every 8 hours
Ceftriaxone Ceftriaxone A broad-spectrum cephalosporin antibiotic and cefotaxime derivative with a very long half-life and high penetrability to meninges, eyes and inner ears. Cephalosporins 1–2 g daily
Ceftaroline Ceftaroline Cephalosporins 600 mg every 12 hours
Azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides 500 mg daily
Clarithromycin Clarithromycin A semisynthetic macrolide antibiotic derived from erythromycin that is active against a variety of microorganisms. It can inhibit protein synthesis in bacteria by reversibly binding to the 50s ribosomal subunits. This inhibits the translocation of aminoacyl transfer-RNA and prevents peptide chain elongation. Macrolides and Ketolides 500 mg twice daily
Doxycycline 100 mg twice daily
Monotherapy Levofloxacin Levofloxacin The l-isomer of ofloxacin. Fluoroquinolones 750 mg daily
Moxifloxacin Moxifloxacin A fluoroquinolone that acts as an inhibitor of DNA topoisomerase II and is used as a broad-spectrum antibacterial agent. Fluoroquinolones 400 mg daily
With strong risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus Add 1 of the following for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus coverage Vancomycin Vancomycin Antibacterial obtained from streptomyces orientalis. It is a glycopeptide related to ristocetin that inhibits bacterial cell wall assembly and is toxic to kidneys and the inner ear. Glycopeptides
Linezolid Linezolid An oxazolidinone and acetamide derived anti-bacterial agent and protein synthesis inhibitor that is used in the treatment of gram-positive bacterial infections of the skin and respiratory tract. Oxazolidinones 600 mg every 12 hours
With strong risk factors for P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas Use an antipneumococcal and antipseudomonal β-lactam Piperacillin Piperacillin Semisynthetic, broad-spectrum, ampicillin derived ureidopenicillin antibiotic proposed for pseudomonas infections. It is also used in combination with other antibiotics. Penicillins tazobactam Tazobactam A penicillanic acid and sulfone derivative and potent beta-lactamase inhibitor that enhances the activity of other anti-bacterial agents against beta-lactamase producing bacteria. Cephalosporins 4.5 g every 6 hours
Cefepime Cefepime A fourth-generation cephalosporin antibacterial agent that is used in the treatment of infections, including those of the abdomen, urinary tract, respiratory tract, and skin. It is effective against pseudomonas aeruginosa and may also be used in the empiric treatment of febrile neutropenia. Cephalosporins 2 g every 8 hours
Ceftazidime Ceftazidime Semisynthetic, broad-spectrum antibacterial derived from cephaloridine and used especially for pseudomonas and other gram-negative infections in debilitated patients. Cephalosporins 2 g every 8 hours
Imipenem Imipenem Semisynthetic thienamycin that has a wide spectrum of antibacterial activity against gram-negative and gram-positive aerobic and anaerobic bacteria, including many multiresistant strains. It is stable to beta-lactamases. Clinical studies have demonstrated high efficacy in the treatment of infections of various body systems. Its effectiveness is enhanced when it is administered in combination with cilastatin, a renal dipeptidase inhibitor. Carbapenems and Aztreonam 500 mg every 6 hours
Meropenem Meropenem A thienamycin derivative antibacterial agent that is more stable to renal dehydropeptidase I than imipenem, but does not need to be given with an enzyme inhibitor such as cilastatin. It is used in the treatment of bacterial infections, including infections in immunocompromised patients. Carbapenems and Aztreonam 1 g every 8 hours
Aztreonam Aztreonam The carbapenems and aztreonam are both members of the bactericidal beta-lactam family of antibiotics (similar to penicillins). They work by preventing bacteria from producing their cell wall, ultimately leading to bacterial cell death. Carbapenems and Aztreonam 2 g every 8 hours
MRSA: methicillin-resistant Staphylococcus aureus

Severe CAP antibiotic regimens (use same dosing from table above):[1,2]

  • If no risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus or P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas, can use either:
    • β-lactam plus a macrolide (preferred)
    • β-lactam plus a respiratory fluoroquinolone
  • If ≥ 2 risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus or P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas are present, add appropriate coverage.

Additional considerations[1,6,23]

  • CAP and influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza: should be given anti-influenza treatment (e.g., oseltamivir Oseltamivir An acetamido cyclohexene that is a structural homolog of sialic acid and inhibits neuraminidase. Antivirals for Influenza) in addition to standard CAP therapy
  • Suspected lung abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease or empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia:
    • Add anaerobic coverage. 
    • Note: Suspected aspiration pneumonia Aspiration pneumonia A type of lung inflammation resulting from the aspiration of food, liquid, or gastric contents into the upper respiratory tract. Pneumonia is not an indication for anaerobic coverage.
  • Other measures:
Table: Considerations in the therapy for CAP[1]
Categrory Recommendations
CAP with influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza Add anti-influenza treatment (e.g., oseltamivir Oseltamivir An acetamido cyclohexene that is a structural homolog of sialic acid and inhibits neuraminidase. Antivirals for Influenza 75 mg twice daily) if the patient tests positive for influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza.
Suspected aspiration pneumonia Aspiration pneumonia A type of lung inflammation resulting from the aspiration of food, liquid, or gastric contents into the upper respiratory tract. Pneumonia Anaerobic coverage is not routinely added.
Suspected lung abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease or empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia Anaerobic coverage is added.
Use of corticosteroids Corticosteroids Chorioretinitis in CAP
CAP: community-acquired pneumonia

Duration of antibiotic therapy[1,4,5,13]

  • Typically ≥ 5 days (both outpatient and inpatient settings)
  • Based on:
    • Improvement of vital signs
    • Mentation
    • Ability to eat
    • Overall clinical condition

Follow-up[1,2,5,6]

  • Repeat chest imaging is not routinely recommended in those with resolution of CAP symptoms within 1 week.
  • If there is no improvement by day 3, or progressive worsening is seen despite receiving antibiotics, evaluate for:
    • Noninfectious etiologies
    • Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease other than pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
    • Nosocomial superinfection
    • Lung abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease or empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia 
    • Resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing to or wrong dose of antibiotics
    • Presence of unsuspected pathogens (e.g., tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis, fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology)
  • Consider consultation (e.g., infectious disease, pulmonology) in cases of nonresolving pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia → may require additional testing, such as bronchoscopic sampling

CAP management checklist

Initial approach:

  • Confirm the diagnosis:
    • Clinical presentation
    • Imaging (chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests and/or chest CT)
    • Laboratory tests, if indicated
  • Determine setting of treatment using PSI (or CURB-65):
    • Outpatient treatment → assess comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus and discharge on recommended oral antibiotics
    • Inpatient treatment → continue risk evaluation and proceed with further laboratory workup as indicated

Inpatient management:

  • Determine the severity of pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia:
    • Shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock or need for vasopressor Vasopressor Acute Cholangitis support and/or requiring mechanical ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing → admit to ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus and treat as severe pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
    • ≥ 3 of the minor criteria (confusion, tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children, hypothermia Hypothermia Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Hypothermia, hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension, multilobar infiltrates, PaO2/FiO2 ≤ 250, ↓ WBC, ↓ platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology, BUN ≥ 20) → admit to ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus and treat as severe pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
    • If admission does not meet criteria for severe pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, treat as nonsevere pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia.
  • Determine the risk for MDR pathogens:
    • For severe pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia:
      • Any risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus and/or P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonasobtain cultures  (including nasal PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR)) and add coverage for MDR pathogens to standard regimen
      • De-escalate, as indicated
    • For nonsevere pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia:
      • Prior respiratory isolation of MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus → obtain cultures (including nasal PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR)) and add coverage for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus to standard regimen
      • Prior respiratory isolation of P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas → obtain cultures and add coverage for P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas to standard regimen
      • Recent hospitalization Hospitalization The confinement of a patient in a hospital. Delirium with IV antibiotics and/or validated risk factors for MRSA MRSA A strain of Staphylococcus aureus that is non-susceptible to the action of methicillin. The mechanism of resistance usually involves modification of normal or the presence of acquired penicillin binding proteins. Staphylococcus and/or P. aeruginosa P. aeruginosa A species of gram-negative, aerobic, rod-shaped bacteria commonly isolated from clinical specimens (wound, burn, and urinary tract infections). It is also found widely distributed in soil and water. P. Aeruginosa is a major agent of nosocomial infection. Pseudomonas → start standard regimen and await culture results before initiating added coverage
      • De-escalate, as indicated
  • If abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease or empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia is suspected → add anaerobic coverage

Complications and Prevention

Complications[2,8]

  • Continuing infection leads to:
    • Loculations ( abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease, empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia) which require drainage and a longer course of antibiotics
    • Destruction of the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy and/or fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans
  • Systemic effects of worsening CAP:
    • Respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure
    • Shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock and multiorgan failure
    • Coagulopathy
    • Exacerbation of comorbidities Comorbidities The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. Comorbidity may affect the ability of affected individuals to function and also their survival; it may be used as a prognostic indicator for length of hospital stay, cost factors, and outcome or survival. St. Louis Encephalitis Virus
    • Metastatic infection (rare) such as brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease or endocarditis Endocarditis Endocarditis is an inflammatory disease involving the inner lining (endometrium) of the heart, most commonly affecting the cardiac valves. Both infectious and noninfectious etiologies lead to vegetations on the valve leaflets. Patients may present with nonspecific symptoms such as fever and fatigue. Endocarditis
    • Death
  • Cardiovascular complications may include myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction and arrhythmias.
  • Nonresolving CAP:
    • Slow response to treatment warrants investigation of individual risk factors and a possible obstructive process (e.g., tumor Tumor Inflammation).
    • Nonresponding CAP in the initial 72 hours can be due to drug resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing, unusual organism or an impaired host defense.

Prevention[2,10–12]

  • Prevention of infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease secondary to S. pneumoniae (pneumococcal vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination):
    • Pneumococcal conjugate vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination (PCV13 or 15):
      • For all children younger than 2 years of age
      • Catch-up vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination schedule given to those who missed shots
    • Pneumococcal conjugate vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination, options include PCV15 (which is followed by pneumococcal polysaccharide vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination [PPSV23]) or PCV20:
      • For all adults ≥ 65 years of age, or 
      • For adults < 65 years at risk for pneumococcal infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
  • Prevention of influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza infection:
    • Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination is recommended: seasonal influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination for all ≥ 6 months of age (who do not have contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation)
    • Chemoprophylaxis Chemoprophylaxis Meningitis in Children:
      • In certain cases (e.g., vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation and high-risk for influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza complications), pre- or post-exposure prophylaxis Prophylaxis Cephalosporins ( oseltamivir Oseltamivir An acetamido cyclohexene that is a structural homolog of sialic acid and inhibits neuraminidase. Antivirals for Influenza or zanamivir Zanamivir A guanido-neuraminic acid that is used to inhibit neuraminidase. Antivirals for Influenza) is given to reduce risk of infection.
      • During influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza outbreaks Outbreaks Sudden increase in the incidence of a disease. The concept includes epidemics and pandemics. Influenza Viruses/Influenza in a hospital or a long-term care facility, empiric antiviral Antiviral Antivirals for Hepatitis B treatment is given to individuals with suspected influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza.
  • Smokers should be encouraged to quit smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases.

Differential Diagnosis

Noninfectious differential diagnoses

  • Pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema: individuals with heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) can present with cough and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, especially on exertion or on lying flat. Peripheral edema Peripheral edema Peripheral edema is the swelling of the lower extremities, namely, legs, feet, and ankles. Edema can be noted, along with S3 S3 Heart Sounds heart sound and elevated jugular venous pressure Jugular Venous Pressure Portal Hypertension. Elevated B-type natriuretic peptide ( BNP BNP A peptide that is secreted by the brain and the heart atria, stored mainly in cardiac ventricular myocardium. It can cause natriuresis; diuresis; vasodilation; and inhibits secretion of renin and aldosterone. It improves heart function. It contains 32 amino acids. Renal Sodium and Water Regulation) and N-terminal pro-BNP (NT-proBNP) is noted. Transthoracic echocardiogram Transthoracic echocardiogram Endocarditis generally reveals a reduced ejection fraction Ejection fraction Cardiac Cycle and systolic (and/or diastolic) dysfunction.
  • Pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism: rarely presents with productive cough or infiltrations visible on chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests, but signs can include tachypnea Tachypnea Increased respiratory rate. Pulmonary Examination and tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children. Examination may also reveal a unilateral leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy swelling Swelling Inflammation. Pulmonary CT angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery confirms the diagnosis.
  • Lung carcinoma: a history of smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, constitutional symptoms Constitutional Symptoms Antineutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis (e.g., significant weight loss Weight loss Decrease in existing body weight. Bariatric Surgery), or chronic cough may be suggestive of lung cancer Lung cancer Lung cancer is the malignant transformation of lung tissue and the leading cause of cancer-related deaths. The majority of cases are associated with long-term smoking. The disease is generally classified histologically as either small cell lung cancer or non-small cell lung cancer. Symptoms include cough, dyspnea, weight loss, and chest discomfort. Lung Cancer. Chest CT, with a subsequent follow-up (after resolution of pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia), is recommended to differentiate consolidation Consolidation Pulmonary Function Tests/infiltrates from a tumor Tumor Inflammation.
  • Interstitial lung disease: cough and shortness of breath Shortness of breath Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea can be manifestations of lung parenchymal conditions including hypersensitivity pneumonitis Pneumonitis Human Herpesvirus 6 and 7, asbestosis Asbestosis A form of pneumoconiosis caused by inhalation of asbestos fibers which elicit potent inflammatory responses in the parenchyma of the lung. The disease is characterized by interstitial fibrosis of the lung, varying from scattered sites to extensive scarring of the alveolar interstitium. Pneumoconiosis, systemic manifestations of rheumatologic diseases ( systemic lupus erythematosus Systemic lupus erythematosus Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus, rheumatoid arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis among others). Historical details, additional lab work-up and chest CT help distinguish other underlying chronic lung diseases from an acute pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia.

Infectious differential diagnoses

  • Acute bronchitis Acute Bronchitis Acute bronchitis is an infection of the mucous membrane of the bronchi without evidence of pneumonia. Due to its pathogenesis, acute bronchitis is frequently accompanied by an upper respiratory tract infection. Cases in which the trachea is also involved are referred to as tracheobronchitis. Acute Bronchitis: infection involving the bronchi Bronchi The larger air passages of the lungs arising from the terminal bifurcation of the trachea. They include the largest two primary bronchi which branch out into secondary bronchi, and tertiary bronchi which extend into bronchioles and pulmonary alveoli. Bronchial Tree: Anatomy, and not the lung parenchyma. Generally, this condition is not associated with abnormal vital signs and/or systemic signs of infection.
  • Acute exacerbation of COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) (AECOPD): characterized by acute worsening of COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) symptoms, which include dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, increased coughing and sputum production. Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease can trigger Trigger The type of signal that initiates the inspiratory phase by the ventilator Invasive Mechanical Ventilation COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) exacerbation.
  • Tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis: pulmonary tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis is caused by Mycobacterium tuberculosis Mycobacterium tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis, and manifests as cough and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea. Weight loss Weight loss Decrease in existing body weight. Bariatric Surgery is a common feature. Different factors (travel history, residents of an endemic area, immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis state, work in high-risk settings) help assess risk of developing pulmonary tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis. Diagnosis requires sputum acid-fast bacilli Acid-fast bacilli Mycobacterium ( AFB AFB Mycobacterium), mycobacterial culture and molecular testing.

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