Comparison of the E test with broth microdilution for antifungal susceptibility testing of yeasts

The susceptibilities of 26 recent invasive clinical isolates to amphotericin B (AMP), 5-flucytosine (5FC), fluconazole (FLU) and itraconazole (ITR) were determined by a broth microdilution modification of the NCCLS M27P method and also by E test. Using breakpoint criteria each result was classified as either sensitive (S), intermediate (I) or resistant (R). Taking the optical density (OD)(80) as the standard, the results were further classified into major (M) or minor (m) errors. E test: AMP = OM Om, 5FC = OM 5m, FLU = 1M 12m, ITR = 1M 5m errors. Minimal inhibitory concentrations (MIG): AMP = OM 2m, 5FC = OM Om, FLU = 3M 4m, ITR = 1M 7m errors. The E test was quick and relatively simple to perform. Results using the E test compared favourably with those of the OD80 and it should be suitable for the routine susceptibility testing of yeasts to antifungal agents.