In vitro susceptibilities to yeasts using the ATB® FUNGUS 2 method, compared with Sensititre Yeast One® and standard CLSI (NCCLS) M27-A2 methods

Abstract

The microbroth ATB FUNGUS 2 (ATBF2) method (bioMérieux, La Balme-les Grottes, France), designed for in vitro determination of the susceptibility of Candida spp. and Cryptococcus neoformans to antifungal agents, was evaluated with 100 yeasts and compared with Sensititre Yeast One (SYO; Trek Diagnostic Systems, UK), considering CLSI M27-A2 as the reference method. ATBF2 consists of ready-to-use strips including amphotericin B (AMB), 5-flucytosine, fluconazole and itraconazole for MIC determinations. Reproducibility of ATBF2 was determined. Two quality control strains and a panel of eight Candida isolates were tested five different times with the three methods. The essential agreements within +/-2 log2 dilution between the ATBF2, SYO and M27-A2 methods were assessed. The yeast clinical isolates included were nine species of Candida (n = 80) and C. neoformans (n = 20). Inter- and intra-laboratory reproducibility, tested with the Candida panel, was >or=99%. MICs for the ATCC strains were within the expected ranges with the three methods. Visual and automated readings of ATBF2 presented good concordance, being lower with itraconazole. The overall essential agreements with the M27-A2 method were 94% and 99% for automated ATBF2 and visual ATBF2 readings, respectively. For SYO, the agreement was 91%. Percentages of agreements by drugs (automated ATBF2/visual ATBF2/SYO) were: 5-flucytosine, 97/100/90; AMB, 97/100/85; fluconazole, 93/97/95; and itraconazole, 89/98/95. Disagreement was higher between M27-A2 and SYO than between M27-A2 and ATBF2. ATBF2 is an objective, reproducible and simple method for the accurate determination of MICs of the most common antifungal drugs in yeasts.