[Study of the susceptibility of black yeasts of the Exophiala genus to antifungals using the Sensititre System]

Abstract

Black yeasts belong to a group of dematiaceous fungi which are difficult to classify and identify. One of the genera that cause human infection, mainly phaeohyphomycosis, is Exophiala, which includes the species E. berger, E. castellanii, E. dermatitidis, E. jeanselmei, E. lecanii-corni, E. moniliae, E. pisciphila, E. salmonis and E. spinifera. We carried out a susceptibility study of five of these species (E. castellanii, E.dermatitidis, E, jeanselmei, E. lecanii-corni and E. moniliae), isolated from cutaneous exudates, to the usual antimycotic agents. Strains were cultured on Sabouraud agar and potato-dextrose agar. Species identification was made by conidiogenous microscopic observation and the following characteristics: maximum growth temperature, tolerance to cicloheximide and carbohydrate assimilation. Susceptibility to antimycotic agents (amphotericin B, fluconazole, itraconazole, ketoconazole and 5-fluorocytosine) was determined by the Sensititre YeastOne (Aamar Blue) commercial method. Amphotericin B activity was good for the five tested species, although the MIC for E. jeanselmei was high (1 mg/l. MICs for fluconazole were high for all the species, but only E. moniliae and E. lecanii-corni c be considered resistant. Activity of itraconazole, ketoconazole and 5-fluorocytosine was good.