A 30-year-old intravenous drug user presents with fever (39.4°C), new regurgitant murmur, and multiple septic pulmonary emboli on CT chest. Blood cultures grow Staphylococcus aureus (MSSA). TEE shows a 1.2 cm vegetation on the tricuspid valve. The most appropriate antibiotic regimen is:

• A Nafcillin for 2 weeks (short-course for uncomplicated right-sided MSSA IE) ✓
• B Vancomycin for 6 weeks
• C Nafcillin (or oxacillin) for 6 weeks
• D Daptomycin 6 mg/kg/day for 6 weeks

Explanation

Uncomplicated right-sided native valve infective endocarditis due to MSSA in IV drug users can be treated with a short 2-week course of anti-staphylococcal penicillin (nafcillin or oxacillin) — supported by multiple trials showing equivalent outcomes to 4-week regimens when there are no metastatic complications, no persistent bacteremia, and no left-sided involvement. Vancomycin is reserved for MRSA. Daptomycin is also effective but typically reserved for MRSA or penicillin allergy. Short-course therapy reduces cost and drug-related complications.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.