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Sensitisation of an Azole-Resistant Aspergillus fumigatus Strain containing the Cyp51A-Related Mutation by Deleting the SrbA Gene.

ABSTRACT: Azoles are widely used for controlling fungal growth in both agricultural and medical settings. The target protein of azoles is CYP51, a lanosterol 14-α-demethylase involved in the biosynthesis of ergosterol. Recently, a novel azole resistance mechanism has arisen in pathogenic fungal species Aspergillus fumigatus. Resistant strains contain a 34-bp or 46-bp tandem repeat (TR) in the promoter of cyp51A, and have disseminated globally in a short period of time. In this study, we investigated whether an azole-resistant strain with a 46-bp TR (TR46/Y121F/T289A) could be sensitised to azoles by deletion of srbA, encoding a direct regulator of cyp51A. The loss of SrbA did not affect colony growth or conidia production, but decreased expression of cyp51A. The srbA deletion strain showed hyper-susceptibility to medical azoles as well as azole fungicides, while its sensitivity to non-azole fungicides was unchanged. This is the first demonstration that deletion of a regulator of cyp51A can sensitise an azole-resistant A. fumigatus strain. This finding may assist in the development of new drugs to help combat life-threatening azole-resistant fungal pathogens.

SUBMITTER: Hagiwara D

PROVIDER: S-EPMC5146965 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Non-cyp51A Azole-Resistant Aspergillus fumigatus Isolates with Mutation in HMG-CoA Reductase.

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Project description:Molecular studies have shown that the majority of azole resistance in Aspergillus fumigatus is associated with amino acid substitutions in the cyp51A gene. To obtain insight into azole resistance mutations, the cyp51A gene of 130 resistant and 76 susceptible A. fumigatus isolates was sequenced. Out of 130 azole-resistant isolates, 105 contained a tandem repeat of 34 bp in the promoter region and a leucine-to-histidine substitution in codon 98 (designated TR/L98H). Additionally, in 12 of these TR/L98H resistant isolates, the mutations S297T and F495I were found, and in 1 isolate, the mutation F495I was found. In eight azole-resistant isolates, known azole resistance mutations were detected in codon G54, G138, or M220. In three azole-susceptible isolates, the mutation E130D, L252L, or S400I was found and in 13 azole-susceptible isolates but also in 1 azole-resistant isolate, the mutations F46Y, G98G, M172V, N248T, D255E, L358L, E427K, and C454C were found. All of the nonsynonymous mutations, apart from the mutations in codons G54, G138, and M220 and L98H, were located at the periphery of the protein, as determined by a structural model of the A. fumigatus Cyp51A protein, and were predicted neither to interact with azole compounds nor to affect structural integrity. Therefore, this wide diversity of mutations in the cyp51A gene in azole-susceptible A. fumigatus isolates is not correlated with azole resistance. Based on the Cyp51A protein homology model, the potential correlation of a mutation to azole resistance can be predicted.

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