Prevalence of azole-resistant Aspergillus fumigatus in the environment of Thailand

Abstract

Occurrence of azole-resistant Aspergillus fumigatus (ARAF) in the environment is an emerging problem worldwide, likely impacting on patient treatment. Several resistance mutations are thought to have initially arisen through triazole-based fungicide use in agriculture and subsequently being propagated in a similar manner. Here we investigated the prevalence of ARAF in the environment of Thailand and characterized their susceptibility profiles toward clinically used azole compounds along with underlying resistance mutations. Three hundred and eight soil samples were collected and analyzed, out of which 3.25% (n = 10) were positive for ARAF. All isolates obtained were resistant to itraconazole (MIC ≥ 8 μg/ml), two showed additional increased MIC values toward posaconazole (MIC = 0.5 μg/ml), and one other toward voriconazole (MIC = 2 μg/ml). Sequencing of the respective cyp51A genes revealed that eight of the isolates carried the TR34/L98H allele and those two with elevated MIC values to posaconazole the G54R substitution. Although a clear correlation between the use of triazole-based fungicides and isolation of ARAF strains from agricultural lands could not be established for Thailand, but this study clearly demonstrates the spread of globally observed ARAF strains to the environment of South East Asia.