The microdilution antibiotic susceptibility test. Bacteroides fragilis.

A micro broth-dilution method was developed for the antibiotic susceptibility testing of Bacteroides frgilis. Eighty strains of B. fragilis were tested against six antibiotics using the agar dilution test as the reference method. The microdilution test yielded results in 24 hours, and agreement with the reference test was satisfactory. Certain subspecies-specific patterns of antibiotic susceptibility were observed. However, larger numbers of subspecies should be evaluated before subspeciation of B. fragilis can be used as a reliable predictor of antibiotic susceptibility.