Cardiobacterium hominis: an elusive cause of endocarditis.

Cardiobacterium hominis is a fastidious bacterium of the normal mouth flora. It has rarely been recognised in the past as a human pathogen and has been difficult to recover from the bloodstream. Mistaken diagnoses and delays in therapy have been common. We report a 29-year-old man with C. hominis endocarditis who was initially treated for a presumed collagen-vascular disorder with anti-flammatory drugs. The organism was eventually recovered in brain-heart infusion medium after prolonged incubation, and cure was accomplished with parenteral penicillin. Special blood culturing methods should be used if endocarditis caused by a fastidious organism is clinically suspected.