A 35-year-old intravenous drug user presents with fever (38.8°C), a new pansystolic murmur heard best at the left sternal border that increases on inspiration, and septic pulmonary emboli on CT chest. Three blood cultures grow Staphylococcus aureus. Echocardiography reveals a 12 mm vegetation on the tricuspid valve. The appropriate empirical antibiotic regimen is:
- A IV vancomycin (MRSA coverage until sensitivities known) ✓
- B IV benzylpenicillin (nafcillin not widely available in India)
- C Oral co-amoxiclav and follow-up in 1 week
- D IV ceftriaxone alone
Correct answer: A. IV vancomycin (MRSA coverage until sensitivities known)
Explanation
Right-sided (tricuspid) infective endocarditis in IVDU is most commonly caused by Staphylococcus aureus, with a substantial proportion being MRSA. Empirical therapy should cover MRSA until antibiotic sensitivities are available, making IV vancomycin the drug of choice. If MSSA is confirmed, de-escalation to an anti-staphylococcal penicillin (oxacillin, nafcillin) or cloxacillin is preferred. Ceftriaxone and benzylpenicillin do not adequately cover S. aureus.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.