A 40-year-old IV drug user presents with fever, tricuspid regurgitation murmur, and multiple pulmonary nodular infiltrates. Blood cultures grow Staphylococcus aureus (MSSA). This is right-sided infective endocarditis. The preferred antibiotic regimen is:

• A Vancomycin for 6 weeks
• B Clindamycin for 4 weeks
• C Ceftriaxone for 2 weeks
• D Anti-staphylococcal penicillin (oxacillin/flucloxacillin) for 4–6 weeks ✓

Explanation

MSSA right-sided IE is treated with anti-staphylococcal beta-lactam (oxacillin or flucloxacillin) for 4–6 weeks per ESC/AHA guidelines; beta-lactams are superior to vancomycin for MSSA infections due to better efficacy (DAPTOVAN and observational data). Vancomycin is reserved for MRSA, beta-lactam allergy, or penicillin-resistant strains. Right-sided MSSA IE can sometimes be treated with a short course (2 weeks) if uncomplicated, but 4–6 weeks is the standard.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.