Association of infective endocarditis caused by Abiotrophia defectiva with mycotic aneurysm formation: A case report and the review of the literature.

A 74-year-old woman with a history of mitral valve prolapse with mitral regurgitation was transferred to our hospital due to infective endocarditis. Blood culture revealed Abiotrophia defectiva which is known as a nutritional variant streptococcus. Transesophageal echocardiography revealed posterior leaflet (P2) prolapse due to rupture of tendon chordae with severe mitral regurgitation and vegetation on posterior leaflet. Magnetic resonance imaging (MRI) revealed multiple infarction lesions in left temporal lobe and parietal lobe and mycotic aneurysm formation of right middle cerebral artery. Because A. defectiva cannot be cultured on non-supplemented media, their prevalence may be underreported. Learning objective: A number of causative microorganisms of infective endocarditis have been identified. Streptococci and staphylococci account for 80 % of cases of infective endocarditis. Abiotrophia defectiva does not grow in ordinary growth media and its prevalence may be underreported. It is important to know A. defectiva causes infective endocarditis with mycotic aneurysm formation.