Inoculum preparation for anaerobic susceptibility tests.

The results of anaerobic susceptibility tests performed with inocula prepared directly from agar isolation media and from overnight broth cultures were compared. Altogether, 93.0% of the results with these two inoculum preparations were within one twofold dilution, including 92.5 and 95.6% of the results with Clostridium species and the Bacteroides fragilis group, respectively. Thus, inocula prepared from agar subculture plates resulted in more-timely susceptibility test results. In addition, the test organisms used in this study grew better when the inoculum was prepared directly from agar plates.