Strep gallolyticus

S. gallolyticus is a gram-positive coccus that grows in bile but, unlike enterococci, does not grow in 6.5% sodium chloride, which is the classic laboratory distinction between the two group D organisms. It colonizes the colon, and mucosal disruption by a neoplasm allows entry to the bloodstream, so bacteraemia or endocarditis with this organism is a marker for an underlying colonic lesion — adenoma or carcinoma — in a substantial proportion of cases; some evidence suggests the organism may also promote tumour progression rather than merely exploit it. The examinable rule is simple: S. gallolyticus/bovis in blood means colonoscopy. It causes subacute endocarditis, typically on abnormal valves, and is usually highly penicillin-sensitive, treated with penicillin or ceftriaxone, often with gentamicin. It is also associated with hepatobiliary disease. Contrast with Enterococcus faecalis and faecium, which grow in both bile and hypertonic saline, follow gastrointestinal or genitourinary instrumentation, and are frequently resistant, with VRE treated using linezolid or daptomycin.