Diphtheroid endocarditis in a patient with a prosthetic valve

A case of diphtheroid endocarditis that developed 4 months after mitral valve replacement is described. In the absence of positive blood cultures, the antibiotic therapy administered initially was ineffective. Fever ceased when cephalotin and erythromycin, to which the diphteroid bacilli were sensitive, was started. Fever recurred 1 month later when the offending organism developed resistance to the antibiotics. Due to thrombotic mitral valve obstruction the patient underwent emergency mitral valve replacement several hours after the onset of cardiogenic shock but she died shortly after surgery. This patient, the 35th such case described in the literature, illustrates the difficulties in diagnosis and the importance of early replacement of the infected valve prosthesis, even in the presence of active endocarditis.