Subacute bacterial enocarditis (also called endocarditis lenta) is a type of endocarditis (more specifically, infective endocarditis) usually caused by a form of streptococci bacteria that normally live in the mouth and throat (Streptococcus mutans, mitis, sanguis,or milleri). Other strains of streptococci (bovis and equines) can also cause subacute endocarditis, usually in patients who have a form of gastrointestinal cancer.