In vitro activity of eight antifungal drugs against 116 Exophiala species recovered from wet environments, coldblooded water animals and rare human cases

Najafzadeh M.J., De Hoog G.S., Klaassen C.H. and Meis J.F.


Objectives: The genus Exophiala contains several species that are potentially able to cause infections in immunocompetent humans, such as E. dermatitidis and E. spinifera. However, during the last decades many Exophiala isolates were recovered which consistently caused diseases in cold-blooded animals living in water, mainly vertebrates but also invertebrates. Until today, only very few human infections caused by this group of waterborne associated species have been described. The aim of this study was to test the activity of eight antifungal drugs against 116 clinical and environmental isolates of these, mostly waterborne, Exophiala species.
Methods: In vitro antifungal susceptibilities were determined as described in CLSI document M 38-A2.
Results: Drugs tested, including their range, were: 0.125-16 μg ml-1 of amphotericin B, 2-16 μg ml-1 of fluconazole, ≤0.016-8 μg ml-1 of itraconazole, 0.125-4 μg ml-1 of voriconazole, ≤0.016-0.5 μg ml-1 of posaconazole, 0.125-8 μg ml-1 of Isavuconazole, 0.016-8 μg ml-1 of caspofungin and ≤0.008-2 μg ml-1 of micafun-gin. The resulting MIC 90s for all strains were as follows, in increasing order: micafungin ≤0.008 μg ml-1, itraconazole and posaconazole ≤0.016 μg ml-1, voriconazole, Isavuconazole and caspofungin 0.125 μg ml-1, amphotericin B 0.25 μg ml-1 and fluconazole 4 μg ml-1.
Conclusion: The waterborne group of Exophiala species is susceptible to most current antifungals. Most active drugs are the echino-candin micafungin, and the triazoles posaconazole, itraconazole, voriconazole and Isavuconazole.

    • TIMM 5th (2013)