First Generation Cephalosporins

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Questions and Answers

How does the mechanism of action of cephalosporins lead to bacterial cell lysis?

  • By interfering with bacterial DNA replication, preventing cell division and leading to cell death.
  • By inhibiting the synthesis of essential bacterial proteins, leading to metabolic dysfunction and cell death.
  • By preventing the cross-linking of peptidoglycan in the bacterial cell wall, leading to weakened cell walls and subsequent lysis. (correct)
  • By directly disrupting the bacterial cell membrane, causing immediate leakage of cellular contents.

What is the primary mechanism by which bacteria develop resistance to cephalosporins?

  • Mutation of ribosomal proteins, preventing the cephalosporin from binding.
  • Drug inactivation by beta-lactamases, altered PBP targets, and reduced diffusion through porin channels. (correct)
  • Increased production of peptidoglycan, overwhelming the effects of the antibiotic.
  • Active efflux of the antibiotic out of the bacterial cell, maintaining a low intracellular concentration.

Why is the combination of cefotetan or cefoxitin with alcohol particularly dangerous?

  • Cefotetan and cefoxitin interfere with alcohol metabolism, leading to a build-up of acetaldehyde in the body, causing a disulfiram reaction. (correct)
  • Alcohol directly inhibits the antibacterial action of cefotetan and cefoxitin.
  • The alcohol increases the rate of antibiotic metabolism, leading to subtherapeutic drug levels and treatment failure.
  • Cefotetan and cefoxitin cause the overproduction of alcohol dehydrogenase.

A patient with a known penicillin allergy is prescribed cefazolin. What is the most important consideration regarding this prescription?

<p>Due to the risk of cross-sensitivity (up to 5-15%), alternative antibiotics should be considered. (C)</p> Signup and view all the answers

How does probenecid interact with penicillin antibiotics, and what is the clinical significance of this interaction?

<p>Probenecid increases penicillin blood levels and effects by slowing its renal excretion. (C)</p> Signup and view all the answers

Why is ceftriaxone contraindicated in neonates (0-28 days old)?

<p>Ceftriaxone can cause biliary sludging and kernicterus in neonates. (D)</p> Signup and view all the answers

What is the significance of SPACE organisms in the context of antibiotic resistance and cephalosporin use?

<p>SPACE organisms (Serratia marcescens, Proteus vulgaris, Acinetobacter species, Citrobacter species, and Enterobacter species) exhibit varying degrees of resistance to cephalosporins, particularly in later generations. (C)</p> Signup and view all the answers

A patient with renal impairment requires treatment with a third-generation cephalosporin. Which of the following cephalosporins would be the MOST appropriate choice, requiring no dosage adjustment?

<p>Ceftriaxone (A)</p> Signup and view all the answers

How does the spectrum of activity change as cephalosporins advance from the first to the fourth generation?

<p>Increased activity against gram-negative organisms and decreased activity against gram-positive organisms. (B)</p> Signup and view all the answers

What is the unique characteristic of ceftaroline compared to other beta-lactam antibiotics, and in what clinical scenarios is this particularly relevant?

<p>Ceftaroline is the only beta-lactam with activity against methicillin-resistant <em>Staphylococcus aureus</em> (MRSA), making it useful in skin and soft tissue infections. (A)</p> Signup and view all the answers

Flashcards

Cephalosporin Mechanism

Inhibit bacterial cell wall synthesis by binding to PBPs, preventing peptidoglycan cross-linking, leading to cell lysis.

Cephalosporin Resistance

Drug inactivation by B-lactamases, altered PBP targets, and reduced drug diffusion.

First Generation Cephalosporins

Includes cefazolin and cephalexin, effective against MSSA, Staph epidermidis, Strep, E. coli, and Klebsiella.

Cephalosporin Contraindications

Allergy to penicillins, cephalosporins, or carbapenems (5-15% cross-sensitivity).

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Second Generation Cephalosporins

Includes cefuroxime and cefoxitin, with broader Gram-negative coverage including H. influenzae and some anaerobes.

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Third Generation Cephalosporins (Group X)

Ceftriaxone and cefotaxime (+/- SPACE organisms), used for STI/PID and meningitis. No Pseudomonas.

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Third Generation Cephalosporins (Group Z)

Ceftazidime (+/- avibactam) covers SPACE, ESBL, Pseudomonas, and Bacteroides.

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Fourth Generation Cephalosporins (Cefepime)

Better Gram-positive and Gram-negative coverage than 3rd generation, including Pseudomonas aeruginosa.

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Fifth Generation Cephalosporins (Ceftaroline)

Only beta-lactam with MRSA activity; similar spectrum to ceftriaxone, indicated for SSTIs and CAP.

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Cephalosporin Spectrum Shift

Later generations have increased activity against Gram-negative organisms and decreased activity against Gram-positive organisms.

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Study Notes

  • Cephalosporins are beta-lactam antibiotics that inhibit bacterial cell wall synthesis, leading to bacterial cell lysis.
  • They bind to penicillin-binding proteins (PBPs), preventing the cross-linking of peptidoglycan in the bacterial cell wall.
  • Resistance occurs through drug inactivation by B-lactamases, altered PBP targets, and reduced diffusion through porin channels.
  • Side effects are similar to penicillin's, plus bleeding with cefotetan and cefoxitin.
  • Cefotetan and cefoxitin combined with alcohol can lead to a disulfiram reaction.

First Generation Cephalosporins

  • Includes cefazolin, cephalexin, and cefadroxil.
  • Active against Staphylococcus aureus (MSSA), Staph epidermidis, Strep pyogenes, Strep pneumoniae, E. coli, P. mirabilis, and K. pneumoniae.
  • Contraindications: allergy to penicillins, cephalosporins, or carbapenems (5 - 15% risk of cross sensitivity).
  • Side effects: hypersensitivity reactions (rash, hives, dyspnea, throat swelling), nausea, vomiting, diarrhea, interstitial nephritis, Direct Coombs positive, hemolytic anemia, and seizures (especially with renal dysfunction).
  • Drug interactions: Probenecid increases penicillin blood levels.
  • A combination of ampicillin and allopurinol increases the risk of rash.
  • May decrease the effects of oral contraceptives.

Second Generation Cephalosporins

  • Includes cefaclor, cefuroxime, cefoxitin, and cefotetan.
  • Spectrum of activity: Same as first generation, plus H. influenzae, BLP (beta-lactamase producing) E. coli, K. pneumoniae (better), serratia marcescens, proteus vulgaris, acinetobacter species, citrobacter species, and enterobacter species (SPACE) +/-, and anaerobes (cefotetan and cefoxitin).
  • Drug interactions: Cefotetan + alcohol leads to disulfiram reaction.
  • Cefotetan + cefoxitin has anaerobic coverage.
  • BLP is beta-lactamase producing.

Third Generation Cephalosporins

  • Group X includes ceftriaxone and cefotaxime.
  • Group Z includes ceftazidime, PLUS avibacta, and ceftolozane/tazobactam.
  • Group X spectrum of activity: Mild-mod gram positive, less gram negative than 2nd generation, +/- SPACE, ceftriaxone for STI/PID and meningitis, and no pseudomonas.
  • Group Z spectrum of activity: Poor gram positive, less than gram negative than group X, SPACE, ESBL, psuedomonas, bacteroides (anaerobic).
  • Drug interactions: Calcium + ceftriaxone forms precipitate.
  • Adjust dose in renal impairment (except ceftriaxone).
  • SPACE covers serratia marcescens, proteus vulgaris, acinetobacter species, citrobacter species, and enterobacter species.
  • ESBL is the extended spectrum BL produce E. coli and K. pneumoniae.
  • Do not use ceftriaxone in neonates (0 - 28 days) causes risk of biliary sludging.
  • Biliary sludging is the accumulation of thick bile, made up of bile salts, cholesterol, and calcium bilirubinate, in the gallbladder.
  • Ceftriaxone in neonates can cause kernicterus.
  • Kernicterus is a form of brain damage caused by high levels of unconjugated bilirubin depositing in the basal ganglia and brainstem nuclei. It occurs primarily in neonates.

Fourth Generation Cephalosporins

  • Includes Cefepime (IV).
  • Spectrum of activity: Gram-positive activity better than 3rd generation.
  • Better gram-negative coverage activity versus 3rd generation.
  • Effective against Pseudomonas aeruginosa.
  • Side effects include cefepime mental status change in elderly patients with renal insufficiency.

Fifth Generation Cephalosporins

  • Includes Ceftaroline.
  • Spectrum of activity: Only beta-lactam with MRSA activity.
  • Coverage similar to ceftriaxone (3rd generation group X).
  • Indicated for SSTIs (skin and soft tissue infection), CAP (community-acquired pneumonia, HAP (hospital acquired pneumonia) NOT PSEUDOMONAS

General Information

  • Cephalosporins are bactericidal.
  • As drugs move from 1st to 4th generation, increased activity against gram-negative organisms and decreased activity against gram-positive organisms.

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