Genetic re-identification and antifungal susceptibility testing of Aspergillus section Nigri strains of the BCCM/IHEM collection.

Black Aspergilli are widely distributed in the environment and are frequently reported as causative agents of different types of mycoses. Many taxonomical revisions have been made, and presently 19 different species are accepted. In this study we (re-) identified 123 strains of the Aspergillus niger group of the BCCM/IHEM collection to check for the presence of species other than A. niger in both environmental and clinical samples. The susceptibility for antifungal drugs was compared between A. niger and Aspergillus tubingensis. Strains were identified based on morphological and molecular data and neighbour joining analysis. We revealed the presence of eight different species of this group in our collection. Our results suggest that Aspergillus foetidus, previously shown to be a species closely related to A. niger should not be considered as a separate species, but rather as a variety of A. niger. Furthermore, we found A. tubingensis at the same prevalence than A. niger in clinical samples. Interestingly, A. niger was shown to have a twofold higher sensitivity to treatment with voriconazole and itraconazole than A. tubingensis. These findings underline once more the importance of correct identification up to the species level in clinical isolates.