Abiotrophia endocarditis: case report and review of the literature.

Abiotrophia is a separate genus of gram-positive cocci formerly classified as nutritionally variant streptococci. These organisms cause 1% to 2% of all infective endocarditis. Unlike Enterococcus or viridans group streptococci, these organisms do not usually grow on conventional blood agar plates. Therefore, Abiotrophia endocarditis is often falsely lumped into the category of culture-negative endocarditis. Adequate diagnosis and treatment of this entity requires a high index of suspicion for the organisms, even if cultures are negative. Nutritional supplementation of the growth media and/or newer 16S ribosomal RNA gene sequencing may be necessary to identify Abiotrophia as the causative organism. Specific antimicrobial therapy and continued surveillance are needed to prevent the significant morbidity and mortality associated with this infection.