A 58-year-old man presents with fever and malaise five weeks after mechanical aortic valve replacement. Blood cultures grow coagulase-negative Staphylococcus (Staphylococcus epidermidis), methicillin-resistant. Transoesophageal echo shows a vegetation with a periannular abscess. Which organism was the most likely cause of his endocarditis?
- A Staphylococcus epidermidis, acquired intraoperatively or perioperatively ✓
- B Viridans group streptococci from transient bacteraemia
- C Enterococcus faecalis from genitourinary instrumentation
- D Streptococcus bovis from a gastrointestinal portal
Correct answer: A. Staphylococcus epidermidis, acquired intraoperatively or perioperatively
Explanation
Prosthetic valve endocarditis presenting within 60 days of surgery is classified as early PVE and is caused most commonly by coagulase-negative staphylococci such as S. epidermidis, inoculated at operation or via perioperative lines. These organisms produce biofilm on the prosthesis and frequently cause periannular abscess, dehiscence, or fistula. Viridans streptococci and enterococci dominate late PVE beyond six months, reflecting community-acquired transient bacteraemias.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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