skip to main content

MRSA mecA resistance — MRCPCH TAS MCQ

Instant feedback + full explanation. One question, done properly.

ModerateMicrobiologyMRSA mecA resistanceMRCPCH TAS

A child with osteomyelitis grows Staphylococcus aureus resistant to flucloxacillin and other beta-lactams. Laboratory testing identifies mecA. What is the mechanism of resistance?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Altered penicillin-binding protein PBP2a

mecA encodes PBP2a, an altered penicillin-binding protein with reduced affinity for many beta-lactams. VanA-mediated precursor change is the mechanism of vancomycin resistance in enterococci. The pearl is that resistance mechanism matters when interpreting apparent beta-lactam susceptibility.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; UK antimicrobial guidance principles