A studyin vitroof the sensitivity to antibiotics ofBacteroides fragilis

Abstract

During a two-year period of observationBacteroidesspecies were isolated from specimens of pus and vaginal swabs from 115 patients in this hospital. Thirty-five representative strains proved on examination to beBacteroides 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 byB. fragilisis discussed in the light of the findingsin vitro.

In Vitro Antimicrobial Susceptibility of Anaerobic Bacteria Isolated from Clinical Specimens

“…Bactericidal activity of these antibiotics tended to be inconsistent. These results are in disagreement with those obtained by Ingham et al (12) using a replica-plating technique with velvet pads; however, it is likely that Ingham et al used a smaller inoculuni of bacteria in the inhibitory phase of their test than we did. Moreover, their definition of significant growth was 20 or more colonies in subcultures of plates with no growth or with growth of not more than 19 colonies.…”

Antimicrobial Susceptibilities of Anaerobic Bacteria: Recent Clinical Isolates

“…Our results with penicillin are similar to those of other workers (5,14,18,21,24,32), including the earlier study from this laboratory (18), except that, as with clindamycin, clostridia other than C. perfringens required significantly higher concentrations for inhibition than they did 3 years ago. In general, the organisms in this group that showed in vitro resistance to clindamycin were susceptible to both penicillin and minocycline.…”

Susceptibility of Bacteroides fragilis to Six Antibiotics Determined by Standardized Antimicrobial Disc Susceptibility Testing

“…Penicillin G. Most of the strains tested were relatively resistant to penicillin G ( (6,(8)(9)(10)14). Although the methods differed in all of the above studies, MIC results with e.hloramphenicol, clindamycin, and penicillin G were similar to those rel)orted here.…”