A 35-year-old IV drug user presents with fever, new tricuspid regurgitation murmur, and multiple septic pulmonary emboli on CT. Blood cultures grow Staphylococcus aureus (MSSA). According to ESC/AHA endocarditis guidelines, the standard antibiotic regimen for right-sided native valve infective endocarditis due to MSSA in IV drug users is:
- A IV oxacillin/nafcillin (anti-staphylococcal penicillin) for 2 weeks (simplified regimen) ✓
- B Vancomycin IV for 6 weeks
- C Combination cefazolin + aminoglycoside for 4 weeks
- D Daptomycin IV for 4–6 weeks
Explanation
Right-sided native valve IE due to MSSA in IV drug users without complications (no left-sided involvement, no empyema, no metastatic infection) can be treated with a simplified 2-week IV regimen using cloxacillin/oxacillin (beta-lactamase-stable penicillin) plus optional aminoglycoside for the first 5 days. The ESC 2023 IE guidelines endorse this 2-week regimen as appropriate for uncomplicated right-sided MSSA endocarditis. This simplified approach improves compliance and reduces hospital stay. Vancomycin is reserved for MRSA; daptomycin is an alternative. The IV drug user context with only right-sided involvement (tricuspid) and pulmonary emboli is the key clinical scenario where the 2-week regimen applies.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.