SBE is caused most commonly by streptococci (especially viridans, microaerophilic, anaerobic, and nonenterococcal group D streptococci and enterococci) and less commonly by S aureus, Staphylococcus epidermidis, Gemella morbillorum, Abiotrophia defectiva (formerly, Streptococcus defectivus), Granulicatella species, and fastidious Haemophilus species.