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MRSA Bacteraemia — RACP Adult Medicine MCQ

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ModerateInfectious DiseasesMRSA BacteraemiaRACP Adult Medicine

A 45-year-old Aboriginal man from rural NSW presents with community-acquired MRSA skin and soft tissue infection (purulent abscess). Blood cultures grow MRSA. The isolate is susceptible to trimethoprim-sulfamethoxazole, doxycycline, and clindamycin but resistant to flucloxacillin. What is the most appropriate IV antibiotic for MRSA bacteraemia?

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Correct answer: E — IV vancomycin

For MRSA bacteraemia, IV vancomycin is the first-line treatment in Australia. Target trough AUC/MIC ratio 400-600 (area under the curve dosing is now preferred over trough-based dosing). Duration is minimum 14 days for uncomplicated bacteraemia (negative repeat cultures by 72 hours, no endocarditis, no metastatic foci). Community-associated MRSA (CA-MRSA) is common in Aboriginal communities. TOE should be performed to exclude endocarditis in all cases of S. aureus bacteraemia.

Reference: eTG – 2025 – Antibiotic Guidelines; ACSQHC – 2024 – SAB Clinical Care Standard