A 38-year-old IV drug user presents with fever, chills, and a new murmur. Blood cultures grow Staphylococcus aureus. Echocardiography shows a large vegetation on the tricuspid valve. He has no prosthetic valve and no previous endocarditis. According to ESC 2023 endocarditis guidelines, the minimum duration of antibiotic therapy for native right-sided S. aureus endocarditis without complications is:
- A 6 weeks as for left-sided endocarditis
- B 2 weeks (with IV nafcillin/cloxacillin or daptomycin if MRSA) ✓
- C 4 weeks regardless of response
- D 8 weeks for all IV drug users
Correct answer: B. 2 weeks (with IV nafcillin/cloxacillin or daptomycin if MRSA)
Explanation
Uncomplicated native right-sided S. aureus endocarditis in IV drug users can be treated with a shortened 2-week course of IV beta-lactam (nafcillin, oxacillin) if criteria are met: right-sided only, MSSA, no haematogenous seeding, good clinical response, no extracardiac infection, non-prosthetic valve. This is supported by older prospective trials and ESC/AHA guidelines, making 2-week IV therapy the minimum for uncomplicated right-sided MSSA IE. MRSA requires daptomycin 6 mg/kg/day. Left-sided or complicated endocarditis requires 4–6 weeks.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.