A comparison of susceptibility results of the Bacteroides fragilis group and other anaerobes by traditional MIC results and statistical methods.

Antimicrobial susceptibility is compared by MIC values reflecting activity by weight and/or percentage of strains resistant. This study establishes these parameters in vitro in the traditional fashion and extends analysis statistically for various groups of anaerobic bacteria. Mode MIC, MIC50, MIC90 values and percentage of strains resistant indicated comparable activity for most of the beta-lactams. Geometric and arithmetic MICs suggested ceftizoxime to be the most active beta-lactam. Statistical analysis of all log2 values showed that metronidazole was the most active followed by clindamycin and that ceftizoxime was significantly more active than cefotaxime, piperacillin, ceftriaxone or cefoxitin.