Ubiquitous Distribution of Azole-Resistant Aspergillus fumigatus-Related Species in Outdoor Environments in Japan

Aspergillus fumigatus-related species are responsible for causing aspergillosis, which is a fatal infectious disease. Recently, there has been a series of reports of A. fumigatus-related species that are resistant to azole drugs used in clinical practice for the treatment of fungal infections. Some of these species have been isolated from outdoor environments. Testing the drug susceptibility of the strains from outdoor environments, therefore, is important. In this study, we isolated and cultured 72 strains of A. fumigatus-related species from the outdoor environment in Japan. The isolates identified via morphological observation and molecular phylogenetic analysis were Aspergillus felis, Aspergillus lentulus, Aspergillus pseudoviridinutans, Aspergillus udagawae, and Aspergillus wyomingensis. The results of the drug susceptibility testing revealed that A. felis (6 of 14 strains) and A. pseudoviridinutans (13 of 17 strains) were resistant to itraconazole (ITCZ), with 4 mg/L or higher minimum inhibitory concentrations (MICs). The voriconazole (VRCZ)-resistant strains with 4 mg/L or higher MICs were A. felis (14 of 14), A. lentulus (4 of 4), A. pseudoviridinutans (15 of 17), A. udagawae (23 of 34), A. wyomingensis (1 of 3), and A. pseudoviridinutans (1 of 3). Among them, A. felis (1 of 14) and A. pseudoviridinutans (7 of 17) demonstrated 8 mg/L or higher MICs for ITCZ and VRCZ. These results indicate that A. fumigatus-related species resistant to ITCZ and VRCZ are widely distributed in outdoor environments in Japan.