In vitro susceptibility of 119 yeast isolates to fluconazole, 5-fluorocytosine, amphotericin B and ketoconazole

The in vitro activity of fluconazole was tested against 13 yeast species (119 strains) isolated from clinical specimens during a 3-month period. For comparative purposes, three other antifungal compounds (5-fluorocytosine, amphotericin B and ketoconazole) were also tested. The tests were carried out using a microautomated method previously developed in our laboratory. The method allowed us to determine the minimum inhibitory concentration (MIC) of the four antifungal drugs used. For each of the drugs we utilized different media. The MIC ranges (mg/l) of fluconazole were: 0.04-12.5 for Candida albicans, 0.19-6.25 for Candida parapsilosis, 12.5-50 for Candida krusei, 0.04-100 for Candida tropicalis, 0.04- greater than 100 for Candida glabrata, 0.09- greater than 25 for Cryptococcus neoformans, 0.09-0.78 for Saccharomyces cerevisiae, 6.25- greater than 100 for Trichosporon beigelii and 0.09-0.19 for Blastoschizomyces capitatus (Trichosporon capitatum). The MIC value (mg/l) was 0.39 for Candida guilliermondii and Candida lusitaniae, greater than 100 for Cryptococcus laurentii and 0.09 for the 3 isolates of Torulopsis candida. These results were obtained using the medium recommended for in vitro testing of fluconazole (high-resolution medium) by Pfizer UK.