Antimicrobials USMLE Step 1 Practice Question
A 36-year-old man with acute myelogenous leukemia undergoing induction chemotherapy develops persistent fever to 39.4°C despite seven days of broad-spectrum antibiotics, including piperacillin-tazobactam and vancomycin. His absolute neutrophil count is 200/mm³, and he has an indwelling central venous catheter. Blood cultures drawn from the catheter grow Candida albicans on two separate occasions, and he is started on a potent antifungal agent administered intravenously. Within one hour of the first infusion, he develops shaking rigors, worsening fever, and hypotension with a blood pressure of 88/54 mmHg. Over the following week, his serum creatinine rises from 0.9 mg/dL to 3.4 mg/dL with associated hypokalemia and hypomagnesemia. Which of the following best describes the mechanism of the most likely drug responsible for these findings?
Answer choices
- AInhibition of lanosterol 14-alpha-demethylase
- BConversion to a toxic free radical that damages fungal DNA
- CInhibition of fungal microtubule assembly
- DInhibition of fungal beta-glucan synthesis
- EBinding ergosterol to create membrane poresCorrect answer
- FInhibition of squalene epoxidase in the ergosterol biosynthesis pathway
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