Microbiology MCAT Practice Question
A researcher isolates a Gram-positive bacterium from a wound infection and performs antibiotic susceptibility testing. The organism shows resistance to beta-lactam antibiotics but remains sensitive to vancomycin. Genetic analysis reveals altered penicillin-binding proteins (PBPs) with reduced affinity for beta-lactams. The cell wall structure remains intact despite the PBP modifications. Which of the following best explains this resistance mechanism?
Answer choices
- AProduction of beta-lactamase enzyme that hydrolyzes the beta-lactam ring
- BAltered penicillin-binding proteins with reduced beta-lactam affinity preventing cell wall cross-linking inhibitionCorrect answer
- CActive efflux pumps that remove beta-lactams from the periplasmic space
- DDecreased membrane permeability due to porin loss in the outer membrane
- ERibosomal methylation preventing antibiotic binding to the 50S subunit
- FEnzymatic modification of beta-lactams through acetylation of the amino group on the beta-lactam ring
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