Comparison of the E Test with Broth Microdilution for Antifungal Susceptibility Testing of Yeasts

Abstract

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 = 0M 0m, 5FC = 0M 5m, FLU = 1M 12m, ITR = 1M 5m errors. Minimal inhibitory concentrations (MIC): AMP = 0M 2m, 5FC = 0M 0m, 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.