A 66-year-old man develops fever with positive blood cultures three weeks after mechanical aortic valve replacement. Which organism is the MOST likely cause of this early prosthetic valve endocarditis?
- A Staphylococcus aureus ✓
- B Viridans streptococci
- C Enterococcus faecalis
- D Streptococcus gallolyticus
Correct answer: A. Staphylococcus aureus
Explanation
Early prosthetic valve endocarditis, defined as occurring within 60 days of surgery, results from intraoperative or nosocomial contamination, and Staphylococcus aureus together with coagulase-negative staphylococci predominate. Late prosthetic valve endocarditis (beyond 60 days) mirrors native valve disease, with viridans streptococci, enterococci, and S. aureus as leading causes. Enterococci follow genitourinary or gastrointestinal instrumentation rather than surgery.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.