Infectious disease · USMLE Step 1 and Step 2

Aminoglycosides song

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

Aminoglycosides

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Key points in this song10

Aminoglycosides (gentamicin, tobramycin, amikacin, streptomycin, neomycin) are bactericidal antibiotics that irreversibly bind the 30S ribosomal subunit, causing misreading of mRNA and inhibition of translocation.
They require oxygen-dependent active transport into bacteria, making them ineffective against obligate anaerobes and poorly active in acidic or hypoxic environments (e.g., abscesses).
Synergistic with beta-lactams against gram-negative rods (Pseudomonas, Enterobacteriaceae) and gram-positive organisms (enterococcal endocarditis) by enhancing cell wall permeability for aminoglycoside uptake.
Dose-dependent (concentration-dependent) killing with a prolonged post-antibiotic effect, supporting once-daily dosing to maximize efficacy and reduce toxicity.
Major adverse effect: nephrotoxicity — causes acute tubular necrosis (proximal tubule), is dose-dependent and reversible; monitor creatinine and trough levels.
Major adverse effect: ototoxicity — preferentially damages the cochlea (high-frequency hearing loss first) and vestibular apparatus; irreversible and cumulative, especially with concomitant loop diuretics.
Neomycin is used orally to reduce gut flora before bowel surgery and to treat hepatic encephalopathy by decreasing ammonia-producing bacteria; poor systemic absorption limits toxicity.
Streptomycin is used for tuberculosis (second-line), tularemia, plague, and brucellosis; gentamicin covers gram-negative sepsis and is combined with ampicillin for enterococcal endocarditis.
Aminoglycosides cross the placenta and are pregnancy category D — associated with fetal ototoxicity (eighth cranial nerve damage); avoid in pregnancy when possible.
Resistance mechanisms include plasmid-encoded aminoglycoside-modifying enzymes (acetylation, phosphorylation, adenylation) that reduce drug binding to the 30S subunit.