Characteristics of azole-resistant Aspergillus fumigatus attached to agricultural products imported to Japan

Due to the increase in the number of azole-resistant Aspergillus fumigatus, there is an urgent need of data to predict future trends and prevent further spreading. The intercountry transfer of resistant A. fumigatus on plant bulbs have been reported. We investigated existence and characteristics of resistant isolates attached to agricultural products imported to Japan. We purchased 292 samples in Japan. All samples were screened for the existence of azole-resistant A. fumigatus. For positive isolates, minimum inhibitory concentrations of the drugs were determined. We also analyzed Cyp51A, Hmg1, and Erg6 mutations of these isolates and conducted microsatellite genotyping. Fourteen azole-resistant isolates were detected, of which 13 were cultured from flower bulbs imported from the Netherlands. Among them 5 were from 11 bulbs of Hippeastrum (45.5%), 5 were from 24 bulbs of Gladiolus (20.8%), 2 were from 4 bulbs of Ixia (50.0%), and 1 was from 22 bulbs of Tulipa (4.5%). Only 1 resistant isolate was cultured from the 10 bulbs of Narcissus (10.0%) originating in Japan. Various novel mutations including Y121F/T289A in Cyp51A with no tandem repeat in promoter region were discovered from imported strains. Our study provides important data showing that agricultural imports provide a possible route for their intercontinental spread and raises the concern that strains harboring highly diverse Cyp51A mutations might increase in clinical settings in the future.