Nonfebrile mitral valve endocarditis due to Neisseria subflava.

Native valve endocarditis normally presents with fever and only later in its course demonstrates dysfunction of the affected valve. We describe a case of endocarditis due to Neisseria subflava, a Gram-negative diplococcal saprophyte of the oral cavity, which was unsuspected clinically and found unexpectedly during a mitral valve operation performed for symptomatic prolapse with regurgitation.