Apparent culture-negative endocarditis of the prosthetic valve caused by Cardiobacterium hominis.

To date, there have been fewer than 50 reported cases of endocarditis caused by C hominis. Only six of these involved prosthetic heart valves. To our knowledge, in no previous case has the organism been cultured directly from the valve, an aspect we believe gives our case special relevance. Our case also illustrates the fact that whenever a fastidious organism is thought to be responsible for infective endocarditis, not only blood cultures but also cardiac tissue cultures should be held beyond the customary period of time.