Blood cultures from a 55-year-old man with tricuspid valve endocarditis yield methicillin-sensitive Staphylococcus aureus. Which intravenous agent is the preferred first-line therapy for this infection?
- A Vancomycin
- B Nafcillin ✓
- C Linezolid
- D Daptomycin
Correct answer: B. Nafcillin
Explanation
For MSSA bacteremia and endocarditis, a penicillinase-resistant penicillin such as nafcillin (or flucloxacillin/oxacillin) remains superior to vancomycin, with faster bacteremia clearance and lower mortality. Vancomycin is reserved for true beta-lactam allergy or MRSA. Daptomycin is inactivated by pulmonary surfactant, making it unsuitable for pneumonia but acceptable here if needed.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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