Prevalence, mechanisms and genetic relatedness of the human pathogenic fungus Aspergillus fumigatus exhibiting resistance to medical azoles in the environment of Taiwan

Abstract

Emerging azole resistance in Aspergillus fumigatus poses a serious threat to human health. This nationwide surveillance study investigated the prevalence and molecular characteristics of azole-resistant A. fumigatus environmental isolates in Taiwan, an island country with increasing use of azole fungicides. Of the 2760 air and soil samples screened from 2014 to 2016, 451 A. fumigatus isolates were recovered from 266 samples and 34 isolates from 29 samples displayed resistance to medical azoles (itraconazole, voriconazole or posaconazole). The resistance prevalence was 10.9% and 7.5% in A. fumigatus-positive samples and isolates respectively. Most (29, 85.3%) azole-resistant isolates harboured TR /L98H mutations, which were widely distributed, clustered genetically with clinical isolates, and had growth rates that were similar to those of the wild-type isolates. Microsatellite genotyping revealed both the global spread of the TR /L98H isolates and the occurrence of TR /L98H/S297T/F495I isolates belonging to local microsatellite genotypes. AfuMDR3 and atrF, two efflux transporter genes, were constitutively upregulated in two individual resistant isolates without cyp51A mutations, highlighting their potential roles in azole resistance. These results emphasize the need for periodic environmental surveillance at the molecular level in regions in which azole fungicides are applied, and agricultural fungicide management strategies that generate less selective pressure should be investigated.

Comparison of the Sensititre YeastOne and CLSI M38-A2 Microdilution Methods in Determining the Activity of Amphotericin B, Itraconazole, Voriconazole, and Posaconazole against Aspergillus Species

“…One hundred isolates were evaluated in this study, including 27 A. fumigatus (1 carried the TR 34 /L98H mutations), 23 A. flavus, 13 A. terreus, and 8 A. niger clinical isolates from the National Cheng-Kung University Hospital isolated from 2011 to 2015; 4 A. fumigatus isolates (all carried the TR 34 /L98H mutations) and 2 A. niger clinical isolates from our multicenter collection isolated during 2016 and 2017; and 23 A. fumigatus environmental isolates (7 carried the TR 34 /L98H mutations and 12 carried the TR 34 /L98H/S297T/F495I mutations; both sets of isolates are described as TR 34 /L98H isolates in this study) recovered from 2014 to 2016 from Taiwan for use in our earlier work (13). Aspergillus species were identified by their morphological characteristics and sequence analyses of their internal transcribed spacer (ITS) region and calmodulin genes, and the presence of TR 34 /L98H(/S297T/F495I) mutations in cyp51A in 24 A. fumigatus isolates was confirmed as described previously (13). The cyp51A sequences of 10 A. niger isolates were determined using the PCR primers and conditions described by Hashimoto et al and were compared with the cyp51A sequence of A. niger CBS 513.88 to detect the presence of any substitution(s) (14).…”

Azole resistance in Aspergillus species in Southern Taiwan: An epidemiological surveillance study

“…The phylogenetic analysis was performed on all resistant and randomly selected clinically and environmentally susceptible A fumigatus isolates in the current study. A total of 34 isolates were included from Taiwan and 37 from other countries . The dendrogram was prepared using the unweighted pair group method with an arithmetic mean algorithm using bionumerics v7.5 software (Applied Maths).…”

“…A total of 34 isolates were included from Taiwan and 37 from other countries. [18][19][20][21][22][23][24][25][26] The dendrogram was prepared using the unweighted pair group method with an arithmetic mean algorithm using bionumerics v7.5 software (Applied Maths).…”

Multicenter Study of Azole-Resistant Aspergillus fumigatus Clinical Isolates, Taiwan1

“…We confirmed the presence of azole resistance by using the Clinical Laboratory Standard Institute method (Appendix Table 1) (2). Isolates resistant to >1 medical azoles (itraconazole, voriconazole, posaconazole, and isavuconazole) were defined as azole-resistant A. fumigatus and examined for resistance mechanisms, microsatellite-based phylogenetic relatedness, and growth rates following previously described methods (3,4).…”