Streptococcus bovis

S. bovis is a gram-positive, catalase-negative, gamma or alpha-hemolytic coccus that grows in the bile-esculin agar and is part of the Lancefield group D streptococci (along with Enterococcus). It normally resides in the human gastrointestinal tract. Its clinical importance lies in two classic associations: (1) Bacteremia or endocarditis caused by S. bovis (particularly S. gallolyticus subsp. gallolyticus) is strongly linked to colorectal carcinoma or other GI malignancies/polyps, thought to be due to disruption of the colonic mucosa allowing bacterial translocation, or due to a favorable tumor microenvironment for bacterial adherence and growth. Any patient diagnosed with S. bovis endocarditis or bacteremia should undergo colonoscopy to rule out colorectal cancer. (2) It is a common cause of subacute bacterial endocarditis, particularly in older patients, often affecting previously normal or mildly damaged valves. Unlike Enterococcus, S. bovis is sensitive to penicillin, which is used for treatment. Distinguishing it from Enterococcus is important: S. bovis grows in bile but does NOT grow in high salt (6.5% NaCl) media, whereas Enterococcus does grow in high salt, a key laboratory differentiation point tested on exams.