Cephalosporins

Cephalosporins are a group of bactericidal beta-lactam antibiotics (similar to penicillins Penicillins Beta-lactam antibiotics contain a beta-lactam ring as a part of their chemical structure. Drugs in this class include penicillin G and V, penicillinase-sensitive and penicillinase-resistant penicillins, cephalosporins, carbapenems, and aztreonam. Penicillins) that exert their effects by preventing 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: Overview from producing their cell walls, ultimately leading to cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death. Cephalosporins are categorized by generation and all drug names begin with “cef-” or “ceph-.” Cephalosporins have expanded antimicrobial activity compared with most penicillins Penicillins Beta-lactam antibiotics contain a beta-lactam ring as a part of their chemical structure. Drugs in this class include penicillin G and V, penicillinase-sensitive and penicillinase-resistant penicillins, cephalosporins, carbapenems, and aztreonam. Penicillins, and are more effective against Enterobacteriaceae; some drugs are active against 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 and/or anaerobic species as well. Cephalosporins are often used to treat 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. Structure and Function of the Skin, soft tissue, bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones, lung, urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract, intraabdominal, and pelvic infections caused by susceptible organisms.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Chemistry

Cephalosporin structure

Cephalosporins are members of the beta-lactam drug family and consist of:

  • A beta-lactam ring: a 4-membered ring containing 2 carbons (α and β carbons), a nitrogen, and a carbonyl group (a carbon double-bonded to oxygen)
    • The group in the compound responsible for antibacterial activity
    • Can be hydrolyzed (i.e., broken down) by beta-lactamases, which are produced by certain resistant 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: Overview
    • If the beta-lactam ring is broken, the drug loses its antibacterial properties.
    • All beta-lactams contain a beta-lactam ring.
  • Side chain (R group): 
    • Bound to the α-carbon in the beta-lactam ring
    • Differentiates cephalosporins from each other
    • Responsible for their unique pharmacokinetics Pharmacokinetics Pharmacokinetics is the science that analyzes how the human body interacts with a drug. Pharmacokinetics examines how the drug is absorbed, distributed, metabolized, and excreted by the body. Pharmacokinetics and Pharmacodynamics and spectra of activity
    • Certain structures can sterically inhibit the hydrolysis of the beta-lactam ring by beta-lactamases. 
  • A 6-membered ring containing both sulfur and nitrogen with a 2nd R group
Structure of beta-lactams

Structure of beta-lactams:
All beta-lactam antibiotics contain the same core 4-membered “beta-lactam” ring (highlighted in red). This ring is responsible for the antibacterial properties of the drug because it is the region that binds to and inhibits the penicillin-binding proteins (PBPs). The PBPs catalyze the formation of the cell wall by generating crosslinks between the peptide chains in the peptidoglycan molecules; PBPs form these crosslinks between acyl-D-Ala-D-Ala peptides, which have a structure similar to the beta-lactam ring.

Image by Lecturio. License: CC BY-NC-SA 4.0

Mechanisms of Action and Resistance

All beta-lactams, including cephalosporins, exert their effects by inhibiting bacterial cell wall synthesis.

Background: understanding cell walls

  • Bacterial cell walls contain peptidoglycan chains (large, thick layers in gram-positive organisms, and relatively smaller/thinner layers in gram-negative organisms).
  • Peptidoglycan chains are composed of:
    • A sugar backbone with 2 alternating sugars: 
      • N-acetylmuramic acid (NAM) 
      • N-acetylglucosamine (NAG)
    • Short, peptide side chains branching off the NAM sugars
  • The short peptides form crosslinked bridges between the adjacent peptidoglycan chains and create a fishnet structure.
    • Crosslinked bridges are necessary for the peptidoglycan (and thus cell wall) structure.
    • Penicillin-binding proteins (PBPs) are enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body's constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes that create these crosslinked bridges.
Structure of bacterial cell walls cephalosporins

Structure of bacterial cell walls

Image by Lecturio. License: CC BY-NC-SA 4.0

Mechanism of action

All beta-lactams work by irreversibly binding to and inhibiting the PBPs → beta-lactam antibiotics inhibit cell wall synthesis.

Bactericidal activity

Beta-lactams, including cephalosporins, have a bactericidal (rather than bacteriostatic) effect. 

  • Bacterial cell wall is necessary for survival → if lacking, cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death is initiated
  • 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: Overview attempt to replicate, they shed their cell walls.
  • In the presence of beta-lactams, however, 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: Overview are unable to form a new cell wall.
  • Bacteria are unable to effectively divide, and the remaining cell autocatalyzes and dies.
Bacteria attempting to divide in the presence of penicillin

Bacterium attempting to divide in the presence of penicillin:
The bacterium sheds its wall and becomes a spheroplast. The spheroplast is unable to survive and autocatalyzes (dies).

Image by Lecturio. License: CC BY-NC-SA 4.0

Mechanisms of resistance

Bacteria use 3 primary mechanisms to resist cephalosporins:

  • Beta-lactamase resistance (cephalosporins are ineffective): 
    • Beta-lactamase is an enzyme that cleaves the beta-lactam ring and inactivates the antibiotic.
    • Cephalosporinases are involved in the case of cephalosporin resistance.
    • Can be produced by both gram-positive and gram-negative organisms
    • Usually secreted
    • May only be secreted in the presence of a beta-lactam antibiotic
    • Most common type of resistance
    • Most gram-negative bacilli possess a beta-lactamase gene.
  • PBP-mediated resistance (↓ cephalosporin binding to PBPs)
    • Mutations in PBPs → ↓ affinity of cephalosporins to PBP 
    • Despite the mutations, these PBPs can produce a cell wall.
  • Porin-mediated resistance (↓ cephalosporin uptake): 
    • Cephalosporins enter 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: Overview through channels called porins in the cell walls.
    • Bacteria can ↓ production of porins → ↓ antibiotic within the cell → antibiotic resistance
    • Common mechanism of resistance in 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 aeruginosa

Beta-lactamase-resistant medications

  • Some medications can overcome beta-lactamases by acting as beta-lactamase inhibitors.
  • Beta-lactamase inhibitors can be combined with beta-lactamase-sensitive cephalosporins to enhance their activity.
  • Beta-lactamase inhibitors include:
    • Tazobactam
    • Avibactam
    • Clavulanic acid (not available in combination with cephalosporins)
    • Sulbactam (not available in combination with cephalosporins)

Pharmacokinetics

Absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption and half-life

  • Oral cephalosporins are rapidly absorbed.
  • Half-lives tend to be short.
    • Most cephalosporins have a half-life < 1 hour and should be dosed every 4 hours in patients with normal renal function.
    • Cephalosporins with longer half-lives:
      • Ceftriaxone (dosed q24 hours)
      • Cefazolin (dosed q8 hours)

Distribution

  • All cephalosporins achieve therapeutic levels in:
    • Pleural fluid
    • Pericardial fluid
    • Peritoneal fluid
    • Synovial fluid
    • Urine
  • Penetration across the blood-brain barrier into the CSF:
    • 1st and 2nd generation: poor
    • 3rd generation (especially ceftriaxone, cefotaxime, and ceftazidime): good with meningeal irritation
  • Protein binding varies significantly between drugs:
    • < 20%: cefalexin, ceftazidime, cefepime, ceftolozane-tazobactam, ceftaroline
    • 20%‒80%: cefuroxime, cefoxitin
    • > 80%: cefazolin, cefotetan, ceftriaxone

Excretion

  • Primarily renal excretion
  • All cephalosporins except ceftriaxone require dose modification in renal failure.

Ceftriaxone precipitation

  • Ceftriaxone can precipitate in the presence of calcium, especially in 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 and kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys.

Thus, ceftriaxone should not be reconstituted/directly mixed with calcium-containing products such as lactated Ringers or total parenteral nutrition (TPN).

Classification

Cephalosporins are generally classified by generation, with the 1st generation drugs being the oldest in this class. Some of the most commonly used drugs are shown in the table below.

Table: Classification of cephalosporins
Generation Parental agents Oral agents
1st generation Cefazolin (Ancef) Cephalexin (Keflex)
2nd generation
  • Cefuroxime
  • Cephamycins (subgroup):
    • Cefotetan
    • Cefoxitin
Cefaclor (Ceclor)
3rd generation
  • Ceftriaxone (Rocephin)
  • Cefotaxime
  • Ceftazidime
  • Cefdinir (Omnicef)
  • Cefixime (Suprax)
4th generation Cefepime None
5th generation and advanced combinations
  • Ceftaroline
  • Ceftolozane
  • Ceftolozane-tazobactam
  • Ceftazidime-avibactam
None

Indications

Activity spectrum

Table: Spectrum of activity of cephalosporins
Drugs Gram-positive cocci Gram-negative bacilli Gram-negative cocci Anaerobes
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, MSSA
  • 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
  • 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 pneumoniae
  • Haemophilus Haemophilus Haemophilus is a genus of Gram-negative coccobacilli, all of whose strains require at least 1 of 2 factors for growth (factor V [NAD] and factor X [heme]); therefore, it is most often isolated on chocolate agar, which can supply both factors. The pathogenic species are H. influenzae and H. ducreyi. Haemophilus influenzae
SPACE organisms 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 Neisseria Neisseria Neisseria is a genus of bacteria commonly present on mucosal surfaces. Several species exist, but only 2 are pathogenic to humans: N. gonorrhoeae and N. meningitidis. Neisseria species are non-motile, gram-negative diplococci most commonly isolated on modified Thayer-Martin (MTM) agar. Neisseriaspp Peptostreptococcus
1st generation
  • Cephalexin
  • Cefazolin
X X* X
2nd generation
  • Cefuroxime
  • Cefaclor
  • Cefoxitin
  • Cefotetan
X X X** X+
3rd generation
  • Ceftriaxone
  • Cefotaxime
  • Ceftazidime
  • Cefdinir
  • Cefixime
X X X++ X X
4th generation
  • Cefepime
X X X X X+
5th generation and combinations:
  • Ceftaroline
  • Ceftolozane-tazobactam
  • Ceftazidime-avibactam
X X X X X+

SPACE organisms: Serratia marcescens, Proteus Proteus Proteus spp. are gram-negative, facultatively anaerobic bacilli. Different types of infection result from Proteus, but the urinary tract is the most common site. The majority of cases are caused by Proteus mirabilis (P. mirabilis). The bacteria are part of the normal intestinal flora and are also found in the environment. Enterobacteriaceae: Proteus mirabilis, Acinetobacter spp., Citrobacter spp., and Enterobacter spp.
*Only non-beta-lactamase-producing species
**Only cephamycins: cefoxitin and cefotetan
+Cefoxitin and ceftolozane-tazobactam are also active against “below the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm anaerobes” Bacteroides Bacteroides Bacteroides is a genus of opportunistic, anaerobic, gram-negative bacilli. Bacteroides fragilis is the most common species involved in human disease and is part of the normal flora of the large intestine. Bacteroides
++Only ceftazidime

Clinical uses

Cephalosporins are used to treat infections caused by susceptible organisms, including:

  • Preoperative prophylaxis against surgical site infections Surgical site infections Surgical site infection (SSI) is a type of surgical infection that occurs at or near a surgical incision within 30 days of the procedure or within 90 days if prosthetic material is implanted. Surgical site infections are classified according to the depth of involvement as superficial, deep, or organ/space. Surgical Site Infections (cefazolin)
  • Skin and soft tissue infections
  • Bone and joint infections
  • Respiratory infections caused by S. pneumoniae and S. pyogenes
    • Upper respiratory infections, including pharyngitis Pharyngitis Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis
    • 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
    • Cystic fibrosis Cystic fibrosis Cystic fibrosis is an autosomal recessive disorder caused by mutations in the gene CFTR. The mutations lead to dysfunction of chloride channels, which results in hyperviscous mucus and the accumulation of secretions. Common presentations include chronic respiratory infections, failure to thrive, and pancreatic insufficiency. Cystic Fibrosis exacerbations
  • Otitis media due to susceptible organisms
  • UTIs due to susceptible gram-negative organisms, especially 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, 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, or Proteus Proteus Proteus spp. are gram-negative, facultatively anaerobic bacilli. Different types of infection result from Proteus, but the urinary tract is the most common site. The majority of cases are caused by Proteus mirabilis (P. mirabilis). The bacteria are part of the normal intestinal flora and are also found in the environment. Enterobacteriaceae: Proteus spp.
  • Sepsis Sepsis Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Sepsis and Septic Shock due to susceptible organisms
  • Bacterial meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis due to Enterobacteriaceae: 3rd- and 4th-generation cephalosporins (therapy of choice)
  • “Below the diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm” infections: cephamycins and 3rd-generation cephalosporins
    • Pelvic inflammatory disease Pelvic inflammatory disease Pelvic inflammatory disease (PID) is defined as a polymicrobial infection of the upper female reproductive system. The disease can affect the uterus, fallopian tubes, ovaries, and adjacent structures. Pelvic inflammatory disease is closely linked with sexually transmitted diseases, most commonly caused by Chlamydia trachomatis, Neisseria gonorrhoeae, and Gardnerella vaginalis. Pelvic Inflammatory Disease
    • Endometritis Endometritis Endometritis is an inflammation of the endometrium, the inner layer of the uterus. The most common subtype is postpartum endometritis, resulting from the ascension of normal vaginal flora to the previously aseptic uterus. Endometritis
    • Neisseria Neisseria Neisseria is a genus of bacteria commonly present on mucosal surfaces. Several species exist, but only 2 are pathogenic to humans: N. gonorrhoeae and N. meningitidis. Neisseria species are non-motile, gram-negative diplococci most commonly isolated on modified Thayer-Martin (MTM) agar. Neisseria gonorrhoeae (note: cefoxitin is ineffective against Chlamydia Chlamydia Chlamydiae are obligate intracellular gram-negative bacteria. They lack a peptidoglycan layer and are best visualized using Giemsa stain. The family of Chlamydiaceae comprises 3 pathogens that can infect humans: Chlamydia trachomatis, Chlamydia psittaci, and Chlamydia pneumoniae. Chlamydia trachomatis)

Adverse Effects and Contraindications

Adverse effects

Allergic reactions are the most common adverse effects.

  • IgE-mediated allergic reactions:
    • Present with pruritis, urticaria Urticaria Urticaria is raised, well-circumscribed areas (wheals) of edema (swelling) and erythema (redness) involving the dermis and epidermis with associated pruritus (itch). Urticaria is not a single disease but rather is a reaction pattern representing cutaneous mast cell degranulation. Urticaria (Hives), angioedema Angioedema Angioedema is a localized, self-limited (but potentially life-threatening), nonpitting, asymmetrical edema occurring in the deep layers of the skin and mucosal tissue. The common underlying pathophysiology involves inflammatory mediators triggering significant vasodilation and increased capillary permeability. Angioedema, 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, and/or anaphylaxis
    • Patients with penicillin allergies are more likely to have cephalosporin allergies due to cross-reactivity
      • Most common with 1st- and 2nd-generation cephalosporins due to similarities in their R groups
      • 3rd- to 5th-generation cephalosporins show minimal cross-reactivity.
  • Dermatologic reactions:
    • Morbilliform rash: a maculopapular eruption due to a hypersensitivity reaction
    • Erythema multiforme Erythema multiforme Erythema multiforme (EM) is an acute hypersensitivity reaction characterized by targetoid skin lesions with multiple rings and dusky centers. Lesions may be accompanied by systemic symptoms (e.g., fever) and mucosal lesions (e.g., bullae). Erythema Multiforme: target lesions developing with acute onset
    • Stevens-Johnson syndrome Stevens-Johnson syndrome Stevens-Johnson syndrome (SJS) is a cutaneous, immune-mediated hypersensitivity reaction that is commonly triggered by medications, including antiepileptics and antibiotics. The condition runs on a spectrum with toxic epidermal necrolysis (TEN) based on the amount of body surface area (BSA) involved. Stevens-Johnson Syndrome: a desquamating 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. Structure and Function of the Skin condition involving mucosal surfaces
  • Neurologic reactions:
    • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures (cefepime, especially in the setting of renal impairment)
  • GI and hepatic reactions:
    • Clostridioides difficile colitis 
    • Suppression of gut flora leading to vitamin K deficiency
    • Formation of biliary sludge and pseudocholelithiasis (ceftriaxone, especially in children)
  • Renal reactions:
    • Cephalosporins can potentiate the renal toxicity of aminoglycosides Aminoglycosides Aminoglycosides are a class of antibiotics including gentamicin, tobramycin, amikacin, neomycin, plazomicin, and streptomycin. The class binds the 30S ribosomal subunit to inhibit bacterial protein synthesis. Unlike other medications with a similar mechanism of action, aminoglycosides are bactericidal. Aminoglycosides.
    • Glomerulonephritis is seen in association with allergic reactions.
  • Hematologic reactions:
    • Hemolytic anemia Hemolytic Anemia Hemolytic anemia (HA) is the term given to a large group of anemias that are caused by the premature destruction/hemolysis of circulating red blood cells (RBCs). Hemolysis can occur within (intravascular hemolysis) or outside the blood vessels (extravascular hemolysis). Hemolytic Anemia
    • Neutropenia Neutropenia Neutrophils are an important component of the immune system and play a significant role in the eradication of infections. Low numbers of circulating neutrophils, referred to as neutropenia, predispose the body to recurrent infections or sepsis, though patients can also be asymptomatic. Neutropenia
    • Immune 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

Contraindications

  • All cephalosporins:
    • Hypersensitivity reactions
    • Anaphylactic reactions to penicillins Penicillins Beta-lactam antibiotics contain a beta-lactam ring as a part of their chemical structure. Drugs in this class include penicillin G and V, penicillinase-sensitive and penicillinase-resistant penicillins, cephalosporins, carbapenems, and aztreonam. Penicillins
  • Ceftriaxone-specific contraindications:
    • Hyperbilirubinemia in neonates (especially if premature)
    • Infants < 28 days of age receiving any IV calcium-containing products
  • Use with caution:
    • Patients with elevated INR
    • Other penicillin allergies
    • Seizure disorders
    • Renal impairment

Comparison of Antibiotic Coverage

Comparison based on mechanisms of action

Antibiotics can be classified in several ways. One way is to classify them based on their mechanism of action:

Table: Antibiotics classified by primary mechanism of action
Mechanism Classes of antibiotics
Bacterial cell wall synthesis inhibitors
  • Penicillins
  • Cephalosporins
  • Penems
  • Miscellaneous
Bacterial protein synthesis inhibitors
  • Tetracyclines Tetracyclines Tetracyclines are a class of broad-spectrum antibiotics indicated for a wide variety of bacterial infections. These medications bind the 30S ribosomal subunit to inhibit protein synthesis of bacteria. Tetracyclines cover gram-positive and gram-negative organisms, as well as atypical bacteria such as chlamydia, mycoplasma, spirochetes, and even protozoa. Tetracyclines
  • 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
  • Ketolide
  • Lincosamides Lincosamides The lincosamides, lincomycin and clindamycin, are inhibitors of bacterial protein synthesis. Drugs in this class share the same binding site as that of macrolides and amphenicols; however, they differ in chemical structure. Lincosamides target the 50S ribosomal subunit and interfere with transpeptidation. Lincosamides
  • Streptogramins
  • Linezolid
Agents acting against DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure and/or folate Folate Folate and vitamin B12 are 2 of the most clinically important water-soluble vitamins. Deficiencies can present with megaloblastic anemia, GI symptoms, neuropsychiatric symptoms, and adverse pregnancy complications, including neural tube defects. Folate and Vitamin B12
  • Sulfonamides
  • Trimethoprim Trimethoprim The sulfonamides are a class of antimicrobial drugs inhibiting folic acid synthesize in pathogens. The prototypical drug in the class is sulfamethoxazole. Although not technically sulfonamides, trimethoprim, dapsone, and pyrimethamine are also important antimicrobial agents inhibiting folic acid synthesis. The agents are often combined with sulfonamides, resulting in a synergistic effect. Sulfonamides and Trimethoprim
  • Fluoroquinolones Fluoroquinolones Fluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms. Fluoroquinolones
Antimycobacterial agents Antimycobacterial Agents Antimycobacterial agents represent a diverse group of compounds that have activity against mycobacterial infections, including tuberculosis, leprosy and Mycobacterium avium complex (MAC) disease. The 1st-line agents for tuberculosis are rifampin, isoniazid, pyrazinamide, and ethambutol. Antimycobacterial Agents
  • Anti- 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 agents
  • Antileprosy agents
  • Atypical mycobacterial agents

Comparison based on coverage

Different antibiotics have varying degrees of activity against different 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: Overview. The table below outlines the antibiotics that are active against 3 important classes 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: Overview, including gram-positive cocci, gram-negative bacilli, and anaerobes.

Antibiotic sensitivity chart

Antibiotic sensitivity:
Chart comparing the microbial coverage of different antibiotics for gram-positive cocci, gram-negative bacilli, and anaerobes.

Image by Lecturio. License: CC BY-NC-SA 4.0

References

  1. McCormack, J., Lalji, F. (2019). The “best” antibiotic sensitivity chart. Retrieved July 12, 2021, from https://therapeuticseducation.org/sites/therapeuticseducation.org/files/Antibiotic_Sensitivity_FINAL_Nov_2019.pdf 
  2. Letourneau, A.R. (2019). Beta-lactam antibiotics: Mechanisms of action and resistance and adverse effects. In Bloom, A. (Ed.), UpToDate. Retrieved May 20, 2021, from https://www.uptodate.com/contents/beta-lactam-antibiotics-mechanisms-of-action-and-resistance-and-adverse-effects
  3. Letourneau, A.R. (2019). Cephalosporins. In Bloom, A. (Ed.), UpToDate. Retrieved May 20, 2021, from https://www.uptodate.com/contents/cephalosporins 
  4. Bui, T., and Preuss, C.V. (2021). Cephalosporins. StatPearls. Retrieved July 12, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK551517/ 
  5. Lexicomp, Inc. (2021). Drug Information Sheets, UpToDate, Retrieved July 12, 2021, from:

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