Activity of voriconazole against Candida albicans and Candida krusei isolated since 1984.

With the recent dramatic rise in fluconazole use, there has been an increase in Candida species resistant to that agent. This has led to the clinical development of newer triazoles such as voriconazole that have greater potency and a broader spectrum of activity. We therefore hypothesized that fluconazole-resistant Candida albicans and Candida krusei would be susceptible to voriconazole. Susceptibility testing was performed on 205 isolates of C. albicans collected from 1984 to 1995, and on C. albicans and C. krusei that were identified as fluconazole resistant since 1995. The anti fungal agents used were amphotericin B, 5-flucytosine, itraconazole, ketoconazole, fluconazole and voriconazole. Three C. albicans and 26 C. krusei isolates had a minimum inhibitory concentration (MIC) >/=20 mg/l and were defined as fluconazole resistant. Of these, 28 isolates were susceptible to </=2.5 mg/l voriconazole, with a mean MIC of 0.78 mg/l. The mean amphotericin B MIC for these same strains was 0.98 mg/l. Only one isolate of C. krusei was relatively resistant to voriconazole with a MIC of 5 mg/l. Of these 29 isolates, there were ten amphotericin-resistant strains of C. krusei (MIC>2 mg/l) but all were susceptible to </=2.5 mg/l voriconazole. The higher potency of voriconazole may be useful in the treatment of fluconazole- and amphotericin-resistant C. albicans and C. krusei.