Azole resistance in Aspergillus (A.) fumigatus has increased over the past twenty-five years and increasing amount of evidence has documented that selection of azole-resistant A. fumigatus (ARAf) takes place in the environment. Similarities between medically used azoles and environmentally used azoles (fungicide azoles) for crop and material protection, have prompted the hypothesis that the increased risk of resistance in patients with aspergillosis can be seen as a result of widespread use of fungicide azoles particularly in the agricultural environment.
The current report summarises the occurrence of azole susceptible and resistant A. fumigatus in samples collected in Denmark during three seasons (2020-2022) from different locations and settings, which might be favourable for A. fumigatus or were areas exposed to fungicide azoles. ARAf was present in 20% of 366 tested samples and in 4.2% of 4538 A. fumigatus tested isolates, with highest proportions in flower and compost related samples. No correlation to azole-fungicide concentrations was verified. Genotyping showed clustering of TR-related ARAf and overlap with Danish clinical isolates.
A. fumigatus grew poorly in the field experiment with no post-application change in ARAf proportions. But in microcosmos, a sustained complete or partial inhibition occurred against wild-type A. fumigatus from some of the tested azoles suggesting that azole-fungicides under some conditions may favour growth of ARAf in soil.