In a 65-year-old man with known mitral regurgitation who presents with fever, Osler nodes, positive blood cultures for Streptococcus viridans, and echocardiographic evidence of new moderate mitral regurgitation with vegetations, how many Duke criteria does he meet?

Duke Criteria Assessment

This patient meets two major criteria and three minor criteria (Answer C). 1112

Systematic Breakdown of Criteria

Major Criteria Met (2 total):

1. Blood cultures positive for IE: Two out of three blood cultures grew Streptococcus viridans, which is explicitly listed as a typical microorganism consistent with IE from 2 separate blood cultures. This definitively meets the major microbiological criterion. 1112

2. Echocardiographic evidence of endocardial involvement: The echocardiogram demonstrated vegetations on the mitral valve. The presence of an oscillating intracardiac mass (vegetation) on a valve structure meets the major echocardiographic criterion. 1112

Critical Point About New Valvular Regurgitation:

The new moderate mitral regurgitation does NOT constitute a separate major criterion in this case. The guidelines explicitly state that "new valvular regurgitation (worsening or changing of pre-existing murmur not sufficient)" is required for a major criterion. 111 Since this patient had documented mild mitral regurgitation two years prior, the progression from mild to moderate represents worsening of pre-existing regurgitation, which does not meet the threshold for a major criterion. The vegetation itself already satisfies the echocardiographic major criterion.

Minor Criteria Met (3 total):

1. Predisposing heart condition: Known mitral regurgitation documented on prior ultrasound constitutes a predisposing cardiac condition. 1112

2. Fever: Temperature of 38.7°C exceeds the threshold of >38°C required for this minor criterion. 1112

3. Immunological phenomena: The three painful nodules on the finger pads represent Osler nodes, which are explicitly listed as an immunological phenomenon. 1112

Common Pitfall to Avoid:

Do not count the worsening mitral regurgitation as an additional major criterion when vegetations are already present. The guidelines are clear that worsening of pre-existing murmurs is insufficient—only new valvular regurgitation (meaning regurgitation where none existed before) qualifies as a major criterion. In this case, the patient already had documented mitral regurgitation, so the progression in severity does not add diagnostic value beyond what the vegetation already provides.

Diagnostic Conclusion:

With 2 major + 3 minor criteria, this patient meets the modified Duke criteria for definite infective endocarditis. 1112 The clinical criteria require either: 2 major criteria, OR 1 major + 3 minor criteria, OR 5 minor criteria for definite IE. This patient exceeds the minimum threshold with 2 major and 3 minor criteria.