Cefotetan Susceptibility Testing Against Anaerobic Bacteria From Obstetrical and Gynecologic Sources: Comparison of Five Different Methods

摘要

Five different antibiotic susceptibility methods were utilized to test the effectiveness of cefotetanagainst 200 anaerobic bacteria recovered from patients with obstetrical or gynecological infections. The object of this study was to determine if a more economical and rapid method for anaerobicsusceptibility testing was as acceptable as the reference agar dilution method. The five methodswere: 1) broth disk elution, 2) microbroth technique, 3) a commercially available microbroth technique,4) a commercially available spiral gradient technique, and 5) reference agar dilution. Theminimal inhibitory concentrations (MICs) calculated from the spiral gradient technique were equalto or within one doubling dilution of the reference system in 99.5% of cases, while the percentage forthe commercially available microbroth system was 96.8%, very similar to the microbroth techniqueused in our laboratory that yielded a percentage of 96.3. The disk elution method correlated to thereference agar dilution method in 95.3% cases. While the overall agreement between these techniquesis good, especially for the spiral gradient system, clustering of certain organisms near thebreakpoint of the antibiotic tested results in variability in the labeling of these organisms as susceptibleor resistant. This problem appears to be particularly significant for the disk elution method. Therefore, further refinements in these methods of suscleptibility testing are needed in order toprovide a more clinically useful assessment of the susceptibility or resistance of certain bacterialisolates.