A study in vitro of the sensitivity to antibiotics of Bacteroides fragilis.

During a two-year period of observation Bacteroides species were isolated from specimens of pus and vaginal swabs from 115 patients in this hospital. Thirty-five representative strains proved on examination to be Bacteroides fragilis. Minimal inhibitory and minimal bactericidal concentrations of six antibiotics for these strains were determined. All strains were resistant to streptomycin, neomycin, and polymyxin, slightly sensitive to penicillin and ampicillin, and fully sensitive to tetracycline, chloramphenicol, erythromycin, and lincomycin. The minimum bactericidal concentrations of chloramphenicol, erythromycin, and lincomycin were two to four times the minimal inhibitory concentrations. Tetracycline failed to exert any consistent bactericidal effect.The treatment of patients with infections caused by B. fragilis is discussed in the light of the findings in vitro.