A patient with MRSA bacteremia is started on vancomycin. The drug's mechanism of action involves:
- A Binding to the D-Ala-D-Ala terminus of peptidoglycan precursors, inhibiting transglycosylation and transpeptidation ✓
- B Inhibiting penicillin-binding protein 2a (PBP2a), which is encoded by the mecA gene
- C Inhibiting dihydropteroate synthase in the peptidoglycan synthesis pathway
- D Inserting into the bacterial cell membrane and creating depolarizing pores
Correct answer: A. Binding to the D-Ala-D-Ala terminus of peptidoglycan precursors, inhibiting transglycosylation and transpeptidation
Explanation
Vancomycin binds to the D-Ala-D-Ala terminus of the lipid II peptidoglycan precursor via hydrogen bonding, sterically blocking both transglycosylation (polymerisation) and transpeptidation (cross-linking). This is distinct from beta-lactams which target PBPs. Daptomycin inserts into membranes; sulfonamides target dihydropteroate synthase in folate synthesis, not peptidoglycan.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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