Antimicrobials USMLE Step 1 Practice Question
A 69-year-old man with gram-negative sepsis is treated with gentamicin 5 mg/kg IV daily. After 5 days, he develops rising serum creatinine (2.8 mg/dL) and vertigo with ataxia. Vital signs show BP 128/76, HR 92, RR 18, temperature 37.2°C, and SpO2 98% on room air. Urinalysis reveals muddy brown casts. He denies hearing loss. Which of the following best describes gentamicin's mechanism of action?
Answer choices
- AIrreversible binding of the 30S ribosomal subunit causing misreading of mRNACorrect answer
- BInhibition of dihydropteroate synthase
- CReversible binding of the 50S ribosomal subunit to block translocation
- DBlockade of peptidoglycan cross-linking by penicillin-binding proteins
- EInhibition of DNA dependent RNA polymerase
- FInhibition of dihydrofolate reductase to prevent tetrahydrofolate synthesis
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