Background and Purpose:

Azole resistance in Aspergillus spp. is of significant clinical concern. We aimed to determine azole resistance in A. fumigatus complex from clinical and environmental sources in Pakistan.

Materials and Methods:

144 clinical and 25 environmental A. fumigatus complex isolates from across Pakistan were used for determination of minimum inhibitory concentrations (MICs) for posaconazole, voriconazole and itraconazole by broth microdilution using CLSI standards. For 39 isolates, mutations in the cyp51A gene were determined by sequencing.

Results:

Among the clinical isolates, 13 (9%) had non-wild-type MICs for posaconazole, 1 isolate had non-wild-type MIC (2 µg/ml) for voriconazole and none of the isolates had non-wild-type MICs for itraconazole. Of the environmental isolates, 3 (12%) had non-wild-type MICs to posaconazole, while none of the isolates had non-wild-type MICs for voriconazole or itraconazole. Amongst the 39 isolates sequenced, no commonly known mutations in the cyp51A gene were identified. Several single nucleotide polymorphisms (SNPs) were found in isolates that showed no correlation with the MICs data.

Conclusion:

We found A. fumigatus complex isolates with non-WT MIC profiles and an upward shift in MICs over time in our study. However, mutations in the cyp51A gene were not identified. These signals, while not definitive for resistance, indicate evolving selective pressure and justify continued, systematic surveillance that integrates longitudinal phenotypic testing with targeted genomics.