Aortic Valve Endocarditis Caused by Abiotrophia defectiva: Case Report and Literature Overview

Abiotrophia defectiva or nutritionally variant Streptococcus (NVS) are a rare but important cause of infectious endocarditis, with high rates of bacteriological failure and mortality. We report the case of a 74-year-old man admitted for fever, fatigue and general malaise in the absence of any underlying cardiac, immunosuppressive illness and previous dental manipulations. Transthoracic and transesophageal echocardiogram revealed bacterial vegetation and significant aortic stenosis and regurgitation. Initial blood culture reported gram-positive cocci in chains, subsequently identified as A. defectiva. The patient completed 6 weeks of antibiotic therapy with ampicillin, with a significant decrease of serum inflammatory markers. He refused cardiac surgery and had relapsing endocarditis with positive blood culture for the same pathogen. The patient was then submitted to double-valve cardiac surgery, obtaining a prompt resolution of clinical signs and symptoms, without other relapse or any complications.

Infectious diseases caused by A. defectiva are extremely rare illnesses. Due to the difficult isolation of the pathogen and the slow clinical progression, clinicians should be aware of this bacterium when dealing with blood culture-negative infective endocarditis.