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Prosthetic Valve Endocarditis — RACP Adult Medicine MCQ

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HardInfectious DiseasesProsthetic Valve EndocarditisRACP Adult Medicine

A 65-year-old man with a mechanical aortic valve develops Staphylococcus aureus (MSSA) endocarditis. Which antibiotic regimen is most appropriate for definitive treatment?

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Correct answer: C — Flucloxacillin IV plus rifampicin IV for ≥6 weeks, plus gentamicin IV for 2 weeks

For prosthetic valve endocarditis due to MSSA, eTG and ESC guidelines recommend flucloxacillin (or nafcillin) IV for ≥6 weeks, combined with rifampicin for ≥6 weeks (commenced after initial bacteraemia clearance) and gentamicin for the initial 2 weeks. Rifampicin is critical for prosthetic valve endocarditis as it penetrates biofilm. Rifampicin should not be started until blood cultures are negative to avoid resistance emergence.

Reference: eTG – 2025 – Antibiotic Guidelines; ESC – 2023 – Infective Endocarditis Guidelines