Bacteroides bivius and bacteroides disiens in obstetrical patients: Clinical findings and antimicrobial susceptibilities

Bacteroides bivius and Bacteroides disiens are newly recognized Bacteroides species distinct from B. fragilis. Twenty-nine strains of B. bivius and 3 strains of B. disiens were studied for susceptibility to 8 antimicrobials and for the presence of β-lactamase. These strains had been isolated from the following sites: endometrium-23; wounds-5 (2 from breast abscesses); blood-2; and an unknown source-2. About fifty per cent of the strains were resistant to 16 mg/l of penicillin or cephalothin. Cefoxitin, chloramphenicol, carbenicillin and metronidazole all had good activity against these organisms at achievable blood concentrations. Clindamycin had excellent activity inhibiting all strains at <0.125 mg/l. β-lactamase was detected in 27 of the 32 strains using the chromogenic cephalosporin, nitrocefin, for assay. Four of these Bacteroides isolates were recovered from patients with postpartum endometritis who failed to respond to treatment with large doses of penicillin, and they required clindamycin for cure. These species should be recognized as penicillin-resistant Bacteroides species which can cause serious infections such as endometritis, breast abscess and septicemia.