A 32-year-old IV drug user develops fever, new tricuspid regurgitation murmur, and septic pulmonary emboli. Blood cultures grow Staphylococcus aureus (MRSA). Which therapy is indicated?
- A Vancomycin IV targeting trough 15–20 µg/mL (or AUC/MIC 400–600) ✓
- B Daptomycin IV 6 mg/kg/day as vancomycin is ineffective for tricuspid endocarditis
- C Linezolid 600 mg IV twice daily for 6 weeks with rifampicin
- D Cefazolin IV as MRSA strains are cefazolin susceptible via inoculum effect
Correct answer: A. Vancomycin IV targeting trough 15–20 µg/mL (or AUC/MIC 400–600)
Explanation
AHA 2015 and ESC 2023 infective endocarditis guidelines recommend vancomycin as first-line therapy for MRSA endocarditis, with trough monitoring replaced by AUC/MIC-guided dosing (target AUC 400–600 mg·h/L) per updated ASHP/IDSA guidance to balance efficacy and nephrotoxicity. Daptomycin 6 mg/kg is an alternative, particularly for right-sided MRSA IE in IV drug users, but vancomycin remains standard first-line. Linezolid is bacteriostatic and not recommended for endocarditis. Cefazolin is not used for MRSA.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.