Genetic analysis of azole-resistant Aspergillus fumigatus isolated from domestic and imported tulip bulbs in Japan.

Abstract

Objectives: Azole-resistant Aspergillus fumigatus (ARAF) poses a significant clinical threat and is increasingly being isolated from agricultural environments. ARAF was recently reported to be able to attach to plant bulbs and to cross national borders through international trade. In this study, we investigated the ARAF isolation rate of imported and domestic tulip bulbs that were sold in Japan.

Methods: A. fumigatus was sought from tulip bulbs purchased in Japan. The cyp51A gene was sequenced to determine possession of tandem repeats (TRs) and single nucleotide variants for the isolates. Whole genome analysis was conducted to compare clinical strains, and drug susceptibility testing for itraconazole, voriconazole, and posaconazole were performed.

Results: A total of 129 A. fumigatus strains were isolated from 204 imported Netherlands bulbs purchased in Japan in 2020-2022, whereas 58 strains were isolated from 209 domestic Japanese bulbs. A TR in the cyp51A promoter (azole resistance-related mutation) was detected in 24.0% of the isolates (31/129) from Netherlands bulbs and 51.7% of the isolates (30/58) from Japanese bulbs. Phylogenetic clustering using genomic data of isolates from imported Netherlands and Japanese tulip bulbs showed that TR-harboring and non-TR isolates were clearly separated into different clusters. Japanese bulb isolates with TR were genetically close to environmental and clinical isolates from the Netherlands as well as isolates from bulbs imported from the Netherlands.

Conclusions: The high frequency of ARAF isolation from the bulb bred in Japan was observed through multiple-year survey.