New species of Madurella, causative agents of black-grain mycetoma

Abstract

A new species of nonsporulating fungus, isolated in a case of black-grain mycetoma in Sudan, is described as Madurella fahalii. The species is characterized by phenotypic and molecular criteria. Multigene phylogenies based on the ribosomal DNA (rDNA) internal transcribed spacer (ITS), the partial β-tubulin gene (BT2), and the RNA polymerase II subunit 2 gene (RPB2) indicate that M. fahalii is closely related to Madurella mycetomatis and M. pseudomycetomatis; the latter name is validated according to the rules of botanical nomenclature. Madurella ikedae was found to be synonymous with M. mycetomatis. An isolate from Indonesia was found to be different from all known species based on multilocus analysis and is described as Madurella tropicana. Madurella is nested within the order Sordariales, with Chaetomium as its nearest neighbor. Madurella fahalii has a relatively low optimum growth temperature (30°C) and is less susceptible to the azoles than other Madurella species, with voriconazole and posaconazole MICs of 1 μg/ml, a ketoconazole MIC of 2 μg/ml, and an itraconazole MIC of >16 μg/ml. Since eumycetoma is still treated only with azoles, correct species identification is important for the optimal choice of antifungal therapy.