Infectious disease · USMLE Step 1 and Step 2

Penicillins song

Penicillins - Mechanism, Coverage & Resistance, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Penicillins

Full song on YouTube ↗Spotify ↗

Key points in this song10

Penicillins are beta-lactam antibiotics that inhibit bacterial cell wall synthesis by irreversibly binding penicillin-binding proteins (PBPs), blocking transpeptidation of peptidoglycan cross-links.
The primary mechanism of resistance is bacterial production of beta-lactamase enzymes that hydrolyze the beta-lactam ring; this is overcome by combining penicillins with beta-lactamase inhibitors such as clavulanate, sulbactam, or tazobactam.
Amoxicillin-clavulanate is the drug of choice for human and animal bite wound infections due to coverage of oral flora including Eikenella corrodens and Pasteurella multocida.
Nafcillin, oxacillin, and dicloxacillin are penicillinase-resistant penicillins used for methicillin-sensitive Staphylococcus aureus (MSSA) infections; they are NOT effective against MRSA.
Piperacillin-tazobactam provides the broadest penicillin-class coverage, including Pseudomonas aeruginosa, and is commonly used for hospital-acquired and polymicrobial infections.
The most common hypersensitivity reaction to penicillin is a maculopapular rash; true IgE-mediated anaphylaxis occurs in approximately 0.01–0.05% of patients.
Cross-reactivity between penicillins and cephalosporins is approximately 1–2% due to shared beta-lactam ring structure; carbapenems carry even lower cross-reactivity risk.
Ampicillin causes a characteristic non-allergic maculopapular rash when given to patients with EBV (mononucleosis) infection or CLL, distinguishing it from true penicillin allergy.
Benzathine penicillin G IM is the treatment of choice for primary, secondary, and early latent syphilis, and is the only acceptable treatment for syphilis in pregnancy.
Penicillins are renally excreted and are generally considered safe in pregnancy (Category B); high-dose IV penicillin can cause seizures due to direct CNS toxicity, particularly in patients with renal failure.