Comparison of Etests and Vitek 2® to broth microdilution for the susceptibility testing of Cryptococcus neoformans

Abstract

We determined the susceptibility of 102 clinical isolates Cryptococcus neoformans from Durban, South Africa, to amphotericin B, fluconazole, flucytosine, and voriconazole using broth microdilution (BMD) according to the Clinical and Laboratory Standards Institute M27-A3 document and compared these results with Etest and Vitek 2®. Essential agreement (EA) of Etest and Vitek 2® compared to BMD was determined. Low MICs that were below the epidemiological cutoff values of the 4 antifungal agents tested were demonstrated by all isolates. The EA of Etests for fluconazole, amphotericin, and voriconazole was 95.1%, 83.3%, and 91.2%, respectively, and for Vitek 2® EA for fluconazole, amphotericin, and flucytosine was 97.1%, 95.1%, and 97.1%, respectively. The Vitek 2® showed good agreement with BMD and is a suitable alternative. Etests demonstrated good EA for azoles only. Clinical cryptococcal isolates from Durban remain susceptible to current recommended antifungal therapy.