Mycobacterium

General Characteristics

Basic features

Morphology and properties:

• Straight or slightly curved bacilli Bacilli Shigella
• Growth:
  • Slow-growing bacilli Bacilli Shigella
  • Most species can be cultured on simple substrates using amino acids Amino acids Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins. Basics of Amino Acids and glycerol.
  • Most species grow on blood agar Blood agar Nocardia/Nocardiosis.
• Nonmotile, non-spore-forming bacilli Bacilli Shigella
• Obligate aerobes Obligate aerobes Bacteriology (some are microaerophilic Microaerophilic Helicobacter)
• Catalase Catalase An oxidoreductase that catalyzes the conversion of hydrogen peroxide to water and oxygen. It is present in many animal cells. A deficiency of this enzyme results in acatalasia. Nocardia/Nocardiosis positive
• Facultative intracellular Facultative intracellular Yersinia spp./Yersiniosis bacilli Bacilli Shigella
• Have a characteristic cell wall Cell wall The outermost layer of a cell in most plants; bacteria; fungi; and algae. The cell wall is usually a rigid structure that lies external to the cell membrane, and provides a protective barrier against physical or chemical agents. Cell Types: Eukaryotic versus Prokaryotic ( envelope Envelope Bilayer lipid membrane acquired by viral particles during viral morphogenesis. Although the lipids of the viral envelope are host derived, various virus-encoded integral membrane proteins, i.e. Viral envelope proteins are incorporated there. Virology) that confers several unique properties:
  • Presence of a hydrophobic waxy layer composed of mycolic acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance
  • Linked to a peptidoglycan Peptidoglycan Penicillins layer by a polysaccharide arabinogalactan
  • ↓ Permeability to many drugs and efflux pumps Efflux Pumps Lincosamides
  • Mycobacteria can invade host cells without presenting with any clinical signs.

Staining properties:

• Acid-fast bacilli Bacilli Shigella:
  • Property conferred by mycolic acid Mycolic acid Long fatty acids found in the cell walls of some actinobacteria, including Mycobacterium tuberculosis. Tuberculosis
  • Do not destain by acid alcohol after being stained with aniline dyes
• Gram stain Gram stain Klebsiella:
  • Usually cannot penetrate the waxy cell wall Cell wall The outermost layer of a cell in most plants; bacteria; fungi; and algae. The cell wall is usually a rigid structure that lies external to the cell membrane, and provides a protective barrier against physical or chemical agents. Cell Types: Eukaryotic versus Prokaryotic of the 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 complex (MTBC)
  • Most commonly produce no stain or variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables results

Classification

• Phylum: Actinobacteria
• Family: Mycobacteriaceae
• Genus: Mycobacterium (consists of > 150 species)

Mycobacteria:

• Typical mycobacteria: MTBC species:
  • M. 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 (most important)
  • M. bovis
  • M. africanum
  • M. microti
  • M. canetti
• Atypical, non-tuberculous mycobacteria (NTM):
  • Classified according to the Runyon system
  • Classification is based on growth rate and pigment production.
  • Groups Ⅰ–Ⅲ are slow growing (> 7 days), and group Ⅳ is considered fast growing (< 7 days):
    • Group I: Photochromogens produce pigment in the presence of light.
    • Group II: Scotochromogens produce pigment in the absence of light.
    • Group III: Non-photochromogens lack pigment (includes Mycobacterium avium complex (MAC) 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).
    • Group IV: produce mature colonies in culture media in < 7 days
• Noncultivable: M. leprae complex (M. leprae and M. lepromatosis)
• Saprophytic
• Skin-ulcer types

Most important pathogenic species:

• MTBC causes 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 ( TB TB 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).
• M. leprae complex causes leprosy Leprosy Leprosy, also known as Hansen’s disease, is a chronic bacterial infection caused by Mycobacterium leprae complex bacteria. Symptoms primarily affect the skin and peripheral nerves, resulting in cutaneous manifestations (e.g., hypopigmented macules) and neurologic manifestations (e.g., loss of sensation). Leprosy.
• M. avium and M. intracellulare (known together as M. avium complex (MAC)) cause:
  • Pulmonary 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 similar to TB TB 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
  • Disseminated infections Disseminated infections IL-12 Receptor Deficiency 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 individuals

Pathogenesis

Reservoirs

• M. 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: humans are the only natural reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli.
• M. leprae natural reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli: armadillos
• M. avium and M. intracellulare are found in water and soil.

Transmission

• M. 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 transmission: respiratory droplets Droplets Varicella-Zoster Virus/Chickenpox from patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with active disease
• M. leprae transmission:
  • Direct contact with lesions
  • Inhalation of infectious droplets Droplets Varicella-Zoster Virus/Chickenpox
• MAC transmission:
  • Inhalation into the respiratory tract
  • Ingestion into the GI tract

Virulence Virulence The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its virulence factors. Proteus

• Cell envelope Envelope Bilayer lipid membrane acquired by viral particles during viral morphogenesis. Although the lipids of the viral envelope are host derived, various virus-encoded integral membrane proteins, i.e. Viral envelope proteins are incorporated there. Virology:
  • Major constituent: mycolic acid Mycolic acid Long fatty acids found in the cell walls of some actinobacteria, including Mycobacterium tuberculosis. Tuberculosis
  • Mycolic acid Mycolic acid Long fatty acids found in the cell walls of some actinobacteria, including Mycobacterium tuberculosis. Tuberculosis is attached to glycolipids Glycolipids Lipid attached to carbohydrate, outward-facing. The Cell: Cell Membrane.
  • Glycolipids Glycolipids Lipid attached to carbohydrate, outward-facing. The Cell: Cell Membrane are responsible for “cord formation” on microscopy (grossly corresponds to granuloma formation).
• Catalase-peroxidase: resists host-cell oxidative response
• Sulfatides and trehalose dimycolate: triggers toxicity Toxicity Dosage Calculation
• Lipoarabinomannan ( LAM LAM Tuberous Sclerosis): induces cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response

Host risk factors

• Elderly
• Children
• 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
• Institutionalized patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
• IV drug use
• HIV HIV Anti-HIV Drugs or other immunodeficiencies
• Travel to high-risk regions

General mycobacterial pathophysiology

• In humans, mycobacterial infections Mycobacterial Infections Antimycobacterial Drugs can affect multiple anatomical sites.
• 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 enter through the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and mucosal barriers.
• Pulmonary and cutaneous 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 are the most common.
• 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 with NTM occur most commonly 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 hosts as 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.
• Mycobacteria can colonize their hosts and cause latent 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 without any obvious clinical signs.

M. tuberculosis complex

Epidemiology

• MTBC 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 cause TB TB 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.
• TB TB 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 an airborne disease that affects 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, sometimes, other organs.
• Causes 1.4 million deaths per year worldwide
• 30% of the global population is infected.
• 10% of infected people will develop active disease.
• Leading cause of deaths in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with HIV HIV Anti-HIV Drugs

Pathophysiology

• 1st step is inhalation of aerosol droplets Droplets Varicella-Zoster Virus/Chickenpox.
• Deposition into 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 leads to 3 possible outcomes:
  • Clearance of 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
  • Primary active disease:
    • Proliferation of 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 within 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)
    • Cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response produced by 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 (IL-12 and Il-18) attract other phagocytic cells.
    • A tubercle (granulomatous structure) forms (promoted by TNF-ɑ)
    • Tubercle expands into lung parenchyma → Ghon complex Ghon complex Tuberculosis
    • 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 can then spread to draining lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy → lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy
    • Ghon complex Ghon complex Tuberculosis + lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy/calcification → Ranke complex
    • If spread is not controlled by immune cells, bacteremia Bacteremia The presence of viable bacteria circulating in the blood. Fever, chills, tachycardia, and tachypnea are common acute manifestations of bacteremia. The majority of cases are seen in already hospitalized patients, most of whom have underlying diseases or procedures which render their bloodstreams susceptible to invasion. Glycopeptides with seeding Seeding The local implantation of tumor cells by contamination of instruments and surgical equipment during and after surgical resection, resulting in local growth of the cells and tumor formation. Grading, Staging, and Metastasis of other organs may occur → miliary TB Miliary TB An acute form of tuberculosis in which minute tubercles are formed in a number of organs of the body due to dissemination of the bacilli through the bloodstream. Tuberculosis
    • When 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 erode into airways (caseating granulomas Granulomas A relatively small nodular inflammatory lesion containing grouped mononuclear phagocytes, caused by infectious and noninfectious agents. Sarcoidosis), the patient becomes contagious.
    • Infection may progress to a chronic stage with episodes of healing and subsequent scarring Scarring Inflammation of lesions.
    • Spontaneous eradication is rare.
• Latent infection (clinical (secondary) disease may occur many years later):
  • Lifetime risk of reactivation Reactivation Herpes Simplex Virus 1 and 2: 5%–10%
  • Immunosuppression is a factor in reactivation Reactivation Herpes Simplex Virus 1 and 2.

Clinical presentation

• Pulmonary manifestations associated with systemic symptoms are most common in primary and secondary TB TB 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.
• Miliary (disseminated) TB TB 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 occurs in 15%–20% of cases (usually in children or 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 individuals).

Identification Identification Defense Mechanisms

Sputum:

• 3 specimens, at least 1 early morning
• Acid-fast bacillus Bacillus Bacillus are aerobic, spore-forming, gram-positive bacilli. Two pathogenic species are Bacillus anthracis (B. anthracis) and B. cereus. Bacillus (AFB) smear
• Mycobacterial culture
• Nuclear acid amplification test

Blood or urine mycobacterial culture: in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with HIV HIV Anti-HIV Drugs or 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 individuals

Tuberculin Tuberculin A protein extracted from boiled culture of tubercle bacilli (Mycobacterium tuberculosis). It is used in the tuberculin skin test (tuberculin test) for the diagnosis of tuberculosis infection in asymptomatic persons. Type IV Hypersensitivity Reaction skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions test (TST; PPD (purified protein derivative) or Mantoux test): 

• Intradermal injection of tuberculin Tuberculin A protein extracted from boiled culture of tubercle bacilli (Mycobacterium tuberculosis). It is used in the tuberculin skin test (tuberculin test) for the diagnosis of tuberculosis infection in asymptomatic persons. Type IV Hypersensitivity Reaction antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination
• Can detect active or latent infection
• Measure induration Induration Dermatologic Examination area after 48–72 hours; positive if:
  • > 5 mm in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with HIV HIV Anti-HIV Drugs or immunosuppression, or recent contact with an individual with TB TB 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
  • > 10 mm in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship from high-risk countries, IV drug users, medical and lab workers
  • > 15 mm in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with no known risk factors for TB TB 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

lnterferon-γ release assay ( IGRA IGRA The assay of interferon-gamma released from lymphocytes after their exposure to a specific test antigen, to check for immunologic memory resulting from a previous exposure to the antigen. The amount of interferon-gamma released is usually assayed by an enzyme-linked immunosorbent assay. Tuberculosis): no distinction between active and inactive TB TB 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

M. leprae complex

Epidemiology

• M. leprae complex 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 cause leprosy Leprosy Leprosy, also known as Hansen’s disease, is a chronic bacterial infection caused by Mycobacterium leprae complex bacteria. Symptoms primarily affect the skin and peripheral nerves, resulting in cutaneous manifestations (e.g., hypopigmented macules) and neurologic manifestations (e.g., loss of sensation). Leprosy.
• Prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency is < 1 in 10,000.
• Highest 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 in India, Brazil, Indonesia, Bangladesh, and Nigeria
• Risk factors for acquisition:
  • Close contact with patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with leprosy Leprosy Leprosy, also known as Hansen’s disease, is a chronic bacterial infection caused by Mycobacterium leprae complex bacteria. Symptoms primarily affect the skin and peripheral nerves, resulting in cutaneous manifestations (e.g., hypopigmented macules) and neurologic manifestations (e.g., loss of sensation). Leprosy
  • Armadillo exposure (natural reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli of M. leprae)
  • Elderly
  • Genetic factors
  • Immunosuppression

Pathophysiology

• 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 inhaled or transmitted through direct skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions contact.
• 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 taken up by 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) and disseminated by blood.
• M. leprae spreads to the nerves and skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions, where it proliferates (especially in Schwann cells).
• Leprosy Leprosy Leprosy, also known as Hansen’s disease, is a chronic bacterial infection caused by Mycobacterium leprae complex bacteria. Symptoms primarily affect the skin and peripheral nerves, resulting in cutaneous manifestations (e.g., hypopigmented macules) and neurologic manifestations (e.g., loss of sensation). Leprosy can manifest in different forms and reflects the spectrum of the host immune response.
• Ridley-Jopling classification of leprosy Leprosy Leprosy, also known as Hansen’s disease, is a chronic bacterial infection caused by Mycobacterium leprae complex bacteria. Symptoms primarily affect the skin and peripheral nerves, resulting in cutaneous manifestations (e.g., hypopigmented macules) and neurologic manifestations (e.g., loss of sensation). Leprosy:
  • Tuberculoid (TT)
  • Borderline tuberculoid (BT)
  • Mid-borderline (BB)
  • Borderline lepromatous (BL)
  • Lepromatous (LL)
  • Indeterminate (I)
• Tuberculoid and lepromatous forms are at the 2 ends of the spectrum:
  • Tuberculoid leprosy Tuberculoid Leprosy Antimycobacterial Drugs:
    • Good cellular immune response ( TH1 Th1 A subset of helper-inducer T-lymphocytes which synthesize and secrete interleukin-2; interferon-gamma; and interleukin-12. Due to their ability to kill antigen-presenting cells and their lymphokine-mediated effector activity, th1 cells are associated with vigorous delayed-type hypersensitivity reactions. T cells: Types and Functions response)
    • Delayed-type hypersensitivity Delayed-type hypersensitivity Type IV hypersensitivity reaction, or delayed-type hypersensitivity, is a cell-mediated response to antigen exposure. The reaction involves T cells, not antibodies, and develops over several days. Presensitized T cells initiate the immune defense, leading to tissue damage. Type IV Hypersensitivity Reaction with interferon-γ and macrophage activation Macrophage activation The process of altering the morphology and functional activity of macrophages so that they become avidly phagocytic. It is initiated by lymphokines, such as the macrophage activation factor (maf) and the macrophage migration-inhibitory factor (mmif), immune complexes, C3b, and various peptides, polysaccharides, and immunologic adjuvants. IL-12 Receptor Deficiency
    • Involves the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions (localized) and peripheral nerves Peripheral Nerves The nerves outside of the brain and spinal cord, including the autonomic, cranial, and spinal nerves. Peripheral nerves contain non-neuronal cells and connective tissue as well as axons. The connective tissue layers include, from the outside to the inside, the epineurium, the perineurium, and the endoneurium. Nervous System: Histology
  • Lepromatous leprosy Lepromatous Leprosy Antimycobacterial Drugs:
    • Minimal cellular immune response
    • Humoral (antibody) response (activated by TH2 Th2 A subset of helper-inducer T-lymphocytes which synthesize and secrete the interleukins il-4; il-5; il-6; and il-10. These cytokines influence b-cell development and antibody production as well as augmenting humoral responses. T cells: Types and Functions cells)
    • Extensive skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions involvement
    • Nerve involvement tends to be symmetric

Clinical presentation

• Hypopigmented or reddish skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions patches Patches Vitiligo associated with loss of sensation
• Paresthesia
• Painless wounds in the extremities
• Facial or ear lumps
• Enlarged and tender peripheral nerves Peripheral Nerves The nerves outside of the brain and spinal cord, including the autonomic, cranial, and spinal nerves. Peripheral nerves contain non-neuronal cells and connective tissue as well as axons. The connective tissue layers include, from the outside to the inside, the epineurium, the perineurium, and the endoneurium. Nervous System: Histology
• Ophthalmic injury (corneal abrasions Abrasions Corneal Abrasions, Erosion, and Ulcers/ulcerations, lagophthalmos Lagophthalmos Leprosy)
• Late findings may include facial paralysis, collapsed nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose Anatomy (External & Internal), clawed fingers, foot drop Foot Drop Leprosy, lack of eyelashes/eyebrows.
• Immunological reactions (systemic inflammatory complications) may occur.

Identification Identification Defense Mechanisms

The organism is identified by skin biopsy Skin Biopsy Secondary Skin Lesions:

• Histopathological examination
• 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)

M. avium complex

Epidemiology

• Most commonly acquired from environment (water sources)
• No documented human-to-human transmission
• Commonly affects people with pre-existing lung disease and 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 (AIDS)

Pathophysiology

• Usually presents as pulmonary infection in immunocompetent individuals
• Can present as disseminated disease or localized lymphadenitis Lymphadenitis Inflammation of the lymph nodes. Peritonsillar Abscess in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with AIDS:
  • Risk increases as CD4 count falls below 50
  • MAC infection is one of the AIDS-defining conditions AIDS-defining conditions Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. AIDS-defining Conditions.
  • MAC 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 enter through the GI mucosa and are phagocytosed by 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 in the lamina propria Lamina propria Whipple’s Disease.
  • Lymphatic drainage transports mycobacteria to the abdominal lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy from where they can enter the bloodstream.
  • Spread can occur to many sites: spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy, bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis, and 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 are most common
  • Most signs and symptoms are due to the elaboration of cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response.
  • Rarely the direct cause of death but ↑ the risk of superinfection
  • Localized lymphadenitis Lymphadenitis Inflammation of the lymph nodes. Peritonsillar Abscess:
    • Usually after the initiation of antiretroviral therapy Antiretroviral therapy Antiretroviral therapy (ART) targets the replication cycle of the human immunodeficiency virus (HIV) and is classified based on the viral enzyme or mechanism that is inhibited. The goal of therapy is to suppress viral replication to reach the outcome of undetected viral load. Anti-HIV Drugs
    • Results from the immune reconstitution inflammatory syndrome (IRIS)

Clinical presentation

• Immunocompetent patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship:
  • Older males with chronic obstructive pulmonary disease Pulmonary disease Diseases involving the respiratory system. Blastomyces/Blastomycosis:
    • Cough, 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, upper-lobe infiltrates/cavities
    • Resembles TB TB 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, but less severe
  • Women > 50 years of age with no preexisting history: often presents as 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
• Individuals with AIDS:
  • Disseminated infection:
    • 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, night sweats Night sweats Tuberculosis
    • Abdominal pain Abdominal Pain Acute Abdomen
    • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea
  • Lymphadenitis Lymphadenitis Inflammation of the lymph nodes. Peritonsillar Abscess:
    • Localized lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs node enlargement (abdominal, mediastinal, cervical)
    • 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

Identification Identification Defense Mechanisms

• Mycobacterial blood culture
• Histopathology and culture of the involved sites ( bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis, lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy)