Failure of erythromycin in preventing bacterial endocarditis

Use of oral erythromycin to prevent bacterial endocarditis has been accepted in the treatment of penicillin-allergic patients who required oral or sinusal surgery. A case of Streptococcus sanguis endocarditis, however, developed in a patient following intravenous erythromycin administration during surgery on the maxillary sinus. The organism isolated proved resistant to erythromycin. This isolation of an erythromycin-resistant organism, together with previous reports of the drug's failure in preventing endocarditis in animal models, and recognition of the bacteriostatic action of erythromycin, argue for caution in our current practice of using erythromycin as a single drug therapy to prevent endocarditis in the patient who is allergic to penicillin.