A 45-year-old intravenous drug user presents with fever, new murmur, and embolic phenomena. Blood cultures grow Staphylococcus aureus (MRSA). TTE shows a 1.5 cm vegetation on the tricuspid valve with moderate regurgitation. Which antibiotic regimen is appropriate?

• A Nafcillin 2g IV every 4 hours for 6 weeks
• B Vancomycin IV for 4–6 weeks (with gentamicin for first 2 weeks)
• C Daptomycin 6 mg/kg IV once daily for 4–6 weeks ✓
• D Ceftriaxone 2g IV once daily for 4 weeks

Explanation

MRSA right-sided infective endocarditis (tricuspid valve) is treated with daptomycin (6 mg/kg/day IV) or vancomycin for 4–6 weeks per AHA 2015 Endocarditis guidelines. Daptomycin has demonstrated equivalent outcomes to vancomycin for right-sided IE in clinical trials and is particularly favored for right-sided MRSA endocarditis. Nafcillin is used for MSSA (methicillin-sensitive SA). Ceftriaxone is used for viridans streptococcal and some MSSA native valve endocarditis. Daptomycin is inactivated by pulmonary surfactant and should not be used for pulmonary infections, but is appropriate for right-sided cardiac IE.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.