A novel combination of CYP51A mutations confers pan-azole resistance in Aspergillus fumigatus.
Antimicrob Agents Chemother. 2020 May 18;:
Authors: Macedo D, Brito Devoto T, Pola S, Finquelievich JL, Cuestas ML, García-Effron G
The treatment of invasive and chronic aspergillosis involves triazole drugs. Its intensive use has resulted in the selection of resistant isolates and at present, azole resistance in Aspergillus fumigatus is considered an emerging threat to public health worldwide.The aim of this work is to uncover the molecular mechanism implicated in the azole resistance phenotype of three Aspergillus fumigatus clinical strains isolated from an Argentinian cystic fibrosis patient under long-term triazole treatment.Strain susceptibilities were assessed and CYP51A gene sequences were analyzed. Two of the studied Aspergillus fumigatus strains harbored the TR34-L98H allele. These strains showed high MIC values for all tested triazole (>16.00 μg/ml, 1.00 μg/ml, 1.00 μg/ml and 2.00 μg/ml for itraconazole, isavuconazole, posaconazole and voriconazole, respectively). The third one showed a novel amino acid change (R65K) combined with the TR34-L98H mutations. This new mutation combination induces a pan-azole MIC augment when compared with TR34-L98H mutants (>16 μg/ml, 4.00 μg/ml, 4.00 μg/ml and 8.00 μg/ml for itraconazole, isavuconazole, posaconazole and voriconazole, respectively). The strain harboring the TR34-R65K-L98H allele showed no inhibition halo when voriconazole susceptibility was evaluated by disk diffusion. The effect of these mutations in the azole-resistant phenotype was confirmed by gene replacement experiments. Transformants harboring the TR34-L98H and TR34-R65K-L98H alleles mimicked the azole-resistance phenotype of the clinical isolates while the incorporation of the TR34-R65K and R65K alleles did not significantly increase azole MIC values.This is the first report of the TR34-L98H allele in Argentina. Moreover, a novel CYP51A allele (TR34-R65K-L98H) that induce a panazole MIC augment is described.
PMID: 32423948 [PubMed – as supplied by publisher]