Insight into the Significance of Aspergillus fumigatus cyp51A Polymorphisms

Abstract

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.

In Vivo Selection of a Unique Tandem Repeat Mediated Azole Resistance Mechanism (TR120) inAspergillus fumigatus cyp51A, Denmark

“…Thus, despite a concentration of 4.3 mg/L (within the recommended trough range), potential subtherapeutic levels during the 200 mg 2×/d dosing scheme cannot be ruled out. The F46Y/M172V/E427K substitutions in Cyp51A, found in both susceptible and resistant isolates, have been suggested to play no role or only a minor role in reduced azole susceptibilities ( 12 , 13 ). TRs in the promoter region of cyp51A have previously been linked to increased cyp51A gene expression and MICs because of duplicated srbA transcription factor binding motifs (SRE1 and SRE2) leading to increased expression of cyp51A ( 14 , 15 ).…”

Genome-Wide Comparative Analysis of Aspergillus fumigatus Strains: The Reference Genome as a Matter of Concern

“…This heterogeneity could potentially lead to confusion, so care must be taken in drawing conclusions on different aspects from a single genetic background [ 15 ]. A recent study carried out in our laboratory [ 19 ] showed that the Af293 reference genome belonged to a specific lineage of A. fumigatus strains which harbors five polymorphisms (F46Y, M172V, N248T, D255E, E427K) in cyp51A gene which codes for the azole target. Based on these phylogenetic studies from whole genome sequencing, the other classic reference genome, the A1163 strain, belonged to a different and distant phylogenetic lineage, which implies that both genomes are significantly different.…”

Galleria mellonella for the Evaluation of Antifungal Efficacy against Medically Important Fungi, a Narrative Review

“…[32,33,[45][46][47][48][49][50][51], Aspergillus spp. [13,29,35,[52][53][54][55][56][57][58][59][60][61], Mucorales [62][63][64], Madurella mycetomatis [65][66][67], and other fungal agents [68][69][70]. The contribution of G. mellonella to the evaluation of antifungal drugs will be detailed in the following paragraphs.…”

“…The treatment of G. mellonella infected with Aspergillus spp. has been evaluated in several studies (Table 4) in order to assess intrinsic resistance in specific species [55,56,83], acquired azole resistance in A. fumigatus [53,54], combinations [35,59], and efficacy of non-antifungal drugs [29,57,58,60,61]. A. fumigatus VRZ (10) AMB (3) sertraline (3,10)…”

“…Voriconazole treatment improved survival of larvae infected with a wild-type isolate (40% survival). Isolates with Cyp51A SNPs also responded to voriconazole to a certain extent but showed a 0% survival [54].…”