Penicillin-resistant bacteroides melaninogenicus infection of the mandible.

Oral infections caused by gram-negative anaerobes are now recognized more frequently than in the past because of improved culturing techniques. A case of B melaninogenicus infection secondary to a fractured mandible, in which the organisms were both clinically resistant and insensitive on culture to penicillin, is presented. The organism was also shown to produce beta-lactamase. Clindamycin is appropriate dosage resulted in diarrhea, which precluded its continuation. Erythromycin therapy was curative in this case. In all cases in which the clinical course does not reflect the expected reasonable response to the appropriate antibiotic therapy, bacterial resistance to a drug should be considered, and laboratory testing for resistance and sensitivities should be performed.