Azole Resistance in Aspergillus fumigatus From Diverse Environments in Ohio, United States, Is Primarily Driven by TR34/L98H and TR46/Y121F/T289A Environmental Signatures

Abstract Aspergillus fumigatus is a leading global human fungal pathogen. Triazole antifungal drugs are used in clinical settings, while triazole demethylase inhibitor (DMI) fungicides are widely applied in the environment to combat plant fungal diseases. Environmental exposure to triazole fungicides may drive cross-resistance to clinical triazoles. To address limited data on environmental azole-resistant A fumigatus (ARAF) in the United States, we conducted surveillance across 75 sites in Ohio, including agricultural (57.3%), naturalized (25.3%), urban (16%), and commercial (1.3%) environments. Samples collected comprised air (n = 411), soil (n = 352), and compost (n = 42). Nested polymerase chain reaction of 397 airborne spore samples detected A fumigatus DNA in 62.7%, with 35.5% wild-type, 17.9% tandem repeat (TR), and 9.3% with mixed genotypes. TR genotype distribution did not differ by environment or DMI use. Aspergillus fumigatus was cultured from 18.1% of air samples, with 1.5% positive for ARAF. From soil and compost, A fumigatus was recovered from 41.4% of samples, of which 9.2% were positive for ARAF. Compost yielded higher A fumigatus (83.3%) and ARAF (21.4%) than soil (36.4% and 1.7%, respectively). ARAF prevalence was higher in urban (9.5%) than agricultural (2.8%) or naturalized (1.4%) environments. Generalized linear models suggested that compost and propiconazole exposure were significant predictors of ARAF occurrence. Among 72 ARAF isolates, 50% and 43% carried TR34/L98H and TR46/Y121F/T289A mutations, respectively, suggesting these mutations as key resistance signatures in Ohio environments. These findings identify compost and DMI exposure as a fertile milieu for ARAF development, highlight urban hotspots, and underscore the need for One Health approaches to resistance management.