Which of the following is NOT a minor criterion for the diagnosis of infective endocarditis?

Infective endocarditis is diagnosed using a combination of major and minor criteria established by the Duke criteria. Among the minor criteria, certain clinical features can contribute to the diagnosis but do not definitively confirm it.

Positive blood cultures are considered a major criterion, not a minor one, because their presence strongly indicates the presence of an infectious organism in the bloodstream, which directly supports the diagnosis of infective endocarditis. Minor criteria include iterative symptoms that may suggest an active infection, such as fever, situations that predispose individuals to the condition (such as pre-existing valvular heart disease or the use of intravenous drugs), and evidence of vascular phenomena like embolic manifestations.

Fever, a predisposing condition, and vascular phenomena help suggest the diagnosis when combined with other findings but are insufficient alone without the presence of major criteria to confirm infective endocarditis. Therefore, the correct response highlights that positive blood cultures fall within the major criteria category, thereby making it an incorrect choice when identifying what constitutes a minor criterion.