Molecular Epidemiology of Azole-Resistant Aspergillus fumigatus in Sawmills of Eastern France by Microsatellite Genotyping

Background: Wood chipping has been described as a potential hotspot for the selection of azole-resistant Aspergillus fumigatus (ARAf). We previously reported ARAf isolates in sawmills (Eastern France), most of which contained the TR34/L98H mutation. Methods: To study genotypic relatedness, microsatellite genotyping (short tandem repeat for A. fumigatus (STRAf)) was performed on 41 azole-susceptible A. fumigatus (ASAf) and 23 ARAf isolated from 18 sawmills and two clinical A. fumigatus (sensitive and resistant) isolated from a sinus sample of a woodworker. Results: Fifty-four unique multilocus genotypes (MLGs) were described among the 66 isolates: 13/24 ARAf and 41/42 ASAf. Allelic diversity was higher for ASAf than for ARAf. Among the 24 ARAf, five isolates had their own MLGs. Thirteen ARAf (54%) belonged to the same group, composed of four close MLGs, defined using Bruvo's distance. Thirty-two of the 42 ASAf (76%) had their own MLGs and could not be grouped with the Bruvo's distance cutoff used (0.2). Conclusion: Thus, at a regional scale and in the particular environment of the wood industry, common but also different distinct genotypes, even in the same sawmill, were identified. This suggests that the hypothesis of ARAf clonal expansion from a common strain is probably insufficient to explain genotype emergence and distribution.