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Persistent MRSA Bacteraemia Switch — SCE Infectious Diseases MCQ

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ModerateAntimicrobial StewardshipPersistent MRSA Bacteraemia SwitchSCE Infectious Diseases

A 55-year-old man develops right-sided infective endocarditis with methicillin-resistant Staphylococcus aureus (MRSA). He is an IV drug user. His team starts IV Vancomycin. At day 7, blood cultures remain positive. What should be done?

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Correct answer: A — Switch to IV Daptomycin 8–10 mg/kg daily — persistent MRSA bacteraemia (>5–7 days) despite adequate Vancomycin warrants switching to Daptomycin

Persistent MRSA bacteraemia (>5–7 days) on adequate Vancomycin (with confirmed AUC/MIC 400–600) indicates treatment failure. Daptomycin at high dose (8–10 mg/kg daily) is the recommended switch. The ARREST trial showed no benefit of adding Rifampicin to standard therapy for MRSA bacteraemia WITHOUT prosthetic material. Linezolid is bacteriostatic and not recommended for bacteraemia. Source control (abscess drainage, device removal) should also be reassessed. TOE must be performed (or repeated) to reassess for vegetations and complications.

Reference: BSAC 2023 – MRSA bacteraemia; ARREST Trial 2018 – Lancet