Comparison of clindamycin, metronidazole, and penicillin for the treatment of experimental infections in mice caused by beta-lactamase-producing Bacteroides intermedius.

Turbid saline suspensions (0.35 ml, approximately 10(9) organisms) of a strain of beta-lactamase-producing Bacteroides intermedius were injected subcutaneously into the right groin of ICR male mice. Therapeutic intraperitoneal doses of clindamycin, metronidazole, or penicillin were administered 4 hr later, and thereafter at successive 8-hr intervals for a total of 12 doses. Necropsy with culture of the infection site was performed 4 hr after the final dose. None of 10 clindamycin-treated animals and none of 10 metronidazole-treated animals developed abscesses, and all cultures taken from the injection sites were sterile. Eight of 10 (80%) penicillin-treated animals developed subcutaneous abscesses; B. intermedius was recovered in pure cultures from all abscesses at necropsy. Nine of 10 (90%) untreated control animals inoculated with the same beta-lactamase-producing B. intermedius strain developed abscesses, all of which were culture-positive. The data indicate that treatment with clindamycin and metronidazole prevented the formation of subcutaneous abscesses in mice inoculated with a beta-lactamase-producing strain of B. intermedius. On the other hand, penicillin failed to prevent the formation of abscesses, 80% of which grew the inoculated organism.