In the Duke criteria for infective endocarditis (IE), positive blood cultures with typical organisms (S. aureus, viridans streptococci, HACEK) on separate occasions represent a MAJOR criterion. Which modified Duke minor criterion was added to improve sensitivity for S. bovis group bacteraemia?
- A Single positive blood culture for Staphylococcus lugdunensis
- B Predisposing condition including prior colon cancer or IBD ✓
- C New atrioventricular conduction block on ECG
- D Elevated CRP without fever
Explanation
S. bovis group bacteraemia (now reclassified as S. gallolyticus) is strongly associated with colorectal carcinoma and IBD (colonic mucosal disruption allows bacterial translocation). The 2015 ESC modified Duke criteria added 'predisposing cardiac conditions' and 'predisposing conditions' including GI disease as minor criteria, improving sensitivity. Colonoscopy is mandatory in S. bovis IE. New AV block is an echocardiographic/ECG complication indicating perivalvular extension, classified separately. S. lugdunensis is a coagulase-negative staph with major criterion status only via positive culture on 2+ occasions.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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