Antibiotic susceptibility testing of anaerobic organisms using the agar dilution method: comparison of three techniques.

Three currently used anaerobic susceptibility testing methods were compared: (1) the technique used at the Wadsworth Microbial Diseases Research Laboratory, (2) the technique listed as the reference standard by the National Committee on Clinical Laboratory Standards, and (3) the technique used at the Tufts New England Medical Center. Four-hundred-seventy anaerobic microorganisms, isolated from clinical specimens, were tested against cefoxitin, cefotetan, ceftizoxime, cefotaxime, ceftazidime, imipenem, and clindamycin. Significant differences were noted in mean inhibitory concentrations and percent susceptible at breakpoint among the three techniques used and varied with the antimicrobial agent and species tested.