Insight into the Significance of Aspergillus fumigatus cyp51A Polymorphisms.

Triazole antifungal compounds are the first treatment choice for invasive aspergillosis. However, in the last decade the rate of azole resistance among strains has increased notoriously. The main resistance mechanisms are well defined and mostly related to point mutations of the azole target, 14-α sterol demethylase (), with or without tandem repeat integrations in the promoter. Furthermore, different combinations of five Cyp51A mutations (F46Y, M172V, N248T, D255E, and E427K) have been reported worldwide in about 10% of all isolates tested. The azole susceptibility profile of these strains shows elevated azole MICs, although on the basis of the azole susceptibility breakpoints, these strains are not considered azole resistant. The purpose of the study was to determine whether these polymorphisms (single nucleotide polymorphisms [SNPs]) are responsible for the azole susceptibility profile and whether they are reflected in a poorer azole treatment response that could compromise patient treatment and outcome. A mutant with a deletion was generated and became fully susceptible to all azoles tested. Also, three gene constructions with different combinations of SNPs were generated and reintroduced into an azole-susceptible wild-type (WT) strain (the Δ strain). The alternative model host was used to compare the virulence and voriconazole response of larvae infected with strains with WT or with SNPs. All strains were pathogenic in larvae, although they did not respond similarly to voriconazole therapeutic doses. Finally, the full genomes of these strains were sequenced and analyzed in comparison with those of WT strains, revealing that they belong to different strain clusters or lineages.