Prospective survey of Aspergillus species isolated from clinical specimens and their antifungal susceptibility: A five-year single-center study in Japan.

Aspergillus fumigatus is the most prevalent species that causes aspergillosis. A. fumigatus strains with tandem repeats in the cyp51A promoter have emerged in the environment. Aspergillus species other than A. fumigatus have also been recognized as causative agents of aspergillosis; however, they show lower susceptibility to antifungals compared with A. fumigatus. Therefore, it is important to precisely identify Aspergillus species and determine their antifungal susceptibility. Herein, we collected 119 mold strains isolated from clinical specimens collected at a hospital between November 2013 and December 2018. The collected strains were identified by sequencing several regions, including internal transcribed spacers, and determined their susceptibility to the antifungals itraconazole, voriconazole, and amphotericin B. Of 119 strains, 107 were Aspergillus species, which were identified as A. fumigatus (67), Aspergillus section Nigri (21), A. flavus (7), A. terreus (6), and A. nidulans (6). In Aspergillus section Nigri, the number of A. niger was less than the number of A. welwitschiae and A. tubingensis. Two azole-resistant A. fumigatus samples were included among the isolates. Four of the eight A. tubingensis isolates showed less susceptibility to voriconazole; however, all isolates of A. niger and A. welwitschiae were susceptible to itraconazole and voriconazole. Because of lack of susceptibility data for non-fumigatus Aspergillus and an increasing frequency of antifungal resistance among A. fumigatus, our data along with further surveillance may contribute to determining the frequency and susceptibility of Aspergillus spp. clinical isolates in Japan.

First clinical isolation report of azole-resistant Aspergillus fumigatus with TR34/L98H-type mutation in Japan.

Recently, azole-resistant Aspergillus fumigatus containing a 34-bp or 46-bp tandem repeat in the promoter region of cyp51A combined with amino acid substitution(s) has appeared in the environment worldwide, including several Asian countries. In this study, we isolated the 34-bp tandem repeat-containing azole-resistant A. fumigatus strain OKH50 from a patient in Japan in May 2016. The patient had not been treated with medical azoles before the strain isolation, suggesting that the resistant property was acquired before infection. In addition, the patient had not traveled overseas. Our analysis of short tandem repeats of the strain indicates that the strain is strongly related to the 34-bp tandem repeat-containing isolates from European countries and Asia-Oceania countries but not to susceptible isolates from Japan, suggesting that the strain was introduced from overseas and might spread in Japan.

Azole susceptibility in clinical and environmental isolates of Aspergillus fumigatus from eastern Hokkaido, Japan.

Azole antifungals are used not only clinically for fungal infections but also used as agricultural fungicides. Recently, azole-resistant Aspergillus fumigatus containing a tandem repeat in the promoter region of cyp51A combined with amino acid substitution(s) appears in the environment in Eurasia, especially in several European countries. Although azole fungicides have been used in Japan, especially in Hokkaido, surveillance and characterization of A. fumigatus in Hokkaido have not been reported. In this study, we collected soil samples from farms that used an azole fungicide in the Tokachi area of eastern Hokkaido, isolated 91 A. fumigatus strains, and determined the minimal inhibitory concentrations of medical azoles required for these strains. Moreover, because causative agent A. fumigatus is ubiquitous in the air and acquired from the environment, we collected 22 clinical isolates of A. fumigatus to measure their susceptibility to medical azoles in a hospital in the Tokachi area. Our data show that almost all A. fumigatus isolates retained susceptibility to medical azoles. Clinical isolates OKH34 and OKH6 showed 8 and 2 µg/mL of voriconazole, respectively, as the minimal inhibitory concentration. Both isolates did not contain tandem repeat in cyp51A promoter region. An isolate contained G448S mutation in cyp51A conferring voriconazole resistance, which is the first report from Japan. Our data shows the existence of azole-resistant and low azole-susceptible clinical isolates and highlight the necessity for continuous surveillance in Japan because resistant A. fumigatus strains can arise through clinical or environmental selection or could be introduced from overseas.