Endocarditis due to strain of Cardiobacterium hominis resistant to erythromycin and vancomycin

Endocarditis caused by Cardiobacterium hominis was observed in a penicillin-allergic patient with a prosthetic cardiac valve who had received prophylactic therapy with erythromycin for dental extractions. The organism was resistant to erythromycin and vancomycin, with minimal inhibitory concentrations of 12.5 microgram/ml and 25 microgram/ml, respectively, but was sensitive to penicillin G, tetracycline, cephalexin, and cefaclor. This case suggests that currently recommended antibiotic prophylactic therapy for endocarditis, especially in penicillin-allergic patients, may be inadequate for unusual pathogens such as C hominis.