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Of the anaerobic, nonsporulating, gram-negative bacilli, those of the genus Bacteroides are most frequently associated with serious infections in man. Forty clinical isolates of the species Bacteroides fragilis were tested quantitatively against 24 antibiotics by an agar-dilution method under anaerobic conditions. Clindamycin, the most active antibiotic studied, had a median MIC of 0.19 µg/ml. Rifampin, erythromcyin, lincomycin, and chloramphenicol also inhibited all isolates in clinically attainable concentrations. More than half of the strains tested were resistant to tetracycline. Some isolates were susceptible to penicillin G, ampicillin, carbenicillin, and the cephalosporins, and all were resistant to the aminoglycosides, polymyxins, and semisynthetic penicillinase-resistant penicillins. [ABSTRACT FROM PUBLISHER]

Eight patients with Bacteroides fragilis bacteremia were treated with iv clindamycin. All patients had abdominal surgical disease (four patients) or decubitus ulcers (four patients), and six of them had had antibiotic treatment just before or at the time of bacteremia. Seven patients had favorable clinical and bacteriologic responses to treatment, particularly those who underwent prompt drainage or debridement of localized purulent or necrotic lesions. The eighth patient had a transient bacteremia, and the efficacy of treatment could not be evaluated. Clindamycin is the most active antibiotic in vitro against B. fragilis and is an effective agent in the treatment of B. fragilis bacteremia. [ABSTRACT FROM PUBLISHER]