Development of reference procedures for broth microdilution antifungal susceptibility testing of yeasts with standardized endpoint determination.

Standard guidelines for the broth microdilution antifungal susceptibility testing of amphotericin B, flucytosine, fluconazole, miconazole and itraconazole are reported. These are a modification of the method developed by the National Committee for Clinical Laboratory Standards (NCCLS) on the following two points: standardization of the means of endpoint determination and the inclusion of miconazole and itraconazole in the testing. MIC was determined to be when the positive control had a turbidity of 0.2 at the 630 nm wavelength. The endpoint was 80% inhibition for azoles and 100% inhibition for other drugs. The method provided good reproducibility, and a wide range of MIC distribution was observed in all antifungal agents except amphotericin B.