Establishment of minimum inhibitory concentrations of cefoperazone for control and reference anaerobic organisms.

The minimum inhibitory concentrations of cefoperazone were determined in a collaborative study for eight National Committee for Clinical Laboratory Standards control and reference strains of anaerobic bacteria by agar and microdilution techniques with several types and sources of media. Recommended minimum inhibitory concentrations for the control strains, Bacteroides fragilis ATCC 25285 and Bacteroides thetaiotaomicron ATCC 29741, are 32 to 64 micrograms/ml and 64 micrograms/ml, respectively. Clostridium perfringens ATCC 13124 gave inconsistent results, and no value is recommended. Recommended values for reference strains are presented. Modification of media did not significantly change the minimum inhibitory concentrations.