Infective endocarditis — the diagnosis and the organisms

The modified Duke criteria:

• Definite = 2 major, OR 1 major + 3 minor, OR 5 minor.
• Possible = 1 major + 1 minor, OR 3 minor.
• Major = (1) the blood culture (typical organisms from separate cultures, persistent bacteraemia, or single Coxiella/positive Q-fever serology — S. aureus counts regardless of nosocomial acquisition or removable source); (2) the endocardial involvement on the echo (the vegetation, the abscess, the prosthetic dehiscence) or the new regurgitation.
• Minor = (1) the predisposition; (2) the fever above 38; (3) the vascular phenomena (the emboli, the mycotic aneurysm, the Janeway); (4) the immunological phenomena (the glomerulonephritis, the Osler, the Roth, the rheumatoid factor); (5) the microbiological evidence not meeting the major.

The empirical antibiotics by the scenario:

• The native valve and late prosthetic — cover staphylococci, streptococci, enterococci.
• The prosthetic valve — add coagulase-negative staphylococci cover; early PVE adds MRSA and non-HACEK gram-negatives; rifampin joins after days of effective therapy once bacteraemia clears.
• The intravenous-drug-user and the right-sided — cover S. aureus in all cases (penicillinase-resistant penicillin, vancomycin, or daptomycin per MRSA prevalence, plus gentamicin).^[1]

The principles: the three sets of the cultures before the antibiotics, the empirical then the directed therapy (PVE at least 6 weeks, NVE 2–6 weeks from first effective therapy), the transoesophageal echo for the prosthetic and the abscess, and early surgery without delay for complicated cases — decided by the endocarditis team.