Broth-dilution method for determining the antibiotic susceptibility of anaerobic bacteria.

A broth-dilution method for performing antimicrobial susceptibility tests on anaerobic bacteria has been proposed. The medium used in the test was Schaedler broth, with incubation in a glove box with an atmosphere of 5% CO(2), 10% H(2), and 85% N(2), or in the GasPak system. Minimal inhibitory concentrations for selected antibiotics were determined, under these conditions, by using a conventional twofold dilution scheme for the antibiotics and a "categorization three-tube method" in which two or three clinically significant concentrations of each antibiotic were used. Minimal inhibitory concentrations obtained by both methods were very similar. The categorization method could be used routinely to test the antimicrobial susceptibility of anaerobic bacteria.