Objectives: Azole resistance in Aspergillus fumigatus isolates has been increasingly reported with variable prevalence worldwide and is challenging the effective management of aspergillosis. Here we report the coexistence of both TR34/L98H and TR46/Y121F/T289A resistance mechanisms in azole-resistant A. fumigatus (ARAF) isolates originating from Tanzania, Africa.

Methods: A total of 30 soil and woody debris samples from the surroundings of Kilimanjaro Christian Medical Centre, Moshi, Tanzania, were processed for detection of ARAF isolates and were investigated for susceptibility to itraconazole, voriconazole, posaconazole and isavuconazole. All ARAF isolates were subjected to a real-time PCR assay for detection of mutations and were genotyped by microsatellite typing.

Results: Of the 30 samples, 29 yielded 108 A. fumigatus isolates. Overall, 15 ARAF isolates were obtained, which included 4 ARAF harbouring the TR46/Y121F/T289A mutation and 11 isolates carrying TR34/L98H. All four TR46/Y121F/T289A A. fumigatus isolates showed high MICs of voriconazole (>16 mg/L) and isavuconazole (8 mg/L). In contrast, the 11 TR34/L98H A. fumigatus isolates were pan-azole resistant. The isolates were cross-resistant to azole fungicides. Notably, 20% of environmental samples harboured ARAF and the TR46/Y121F/T289A resistance mechanism was found in 5.5% of the soil samples, where it coexisted with TR34/L98H. The Tanzanian TR46/Y121F/T289A strains had a genotype identical to Dutch clinical TR46/Y121F/T289A isolates.

Conclusions: The present study reports the isolation of resistant A. fumigatus strains harbouring the TR46/Y121F/T289A mutation from Africa. Recovery of TR46/Y121F/T289A from the environment is worrisome and we must strive for effective surveillance of clinical and environmental sources to detect azole resistance in A. fumigatus.