Overexpression of Efflux Pump Genes is an Alternative Mechanism in Voriconazole Resistant Aspergillus fumigatus isolates without Relative Mutations in cyp51A

Author:

Ms Pooja Sen (IN)

Abstract:

Background: The emergence and spread of azole resistance in Aspergillus fumigatus in the environment due to use of azole based pesticides been acknowledged worldwide. While mutations in cyp51A gene are known resistance mechanisms, recent reports highlight strains showing azole resistance without these mutations. Hence, other resistance mechanisms, like efflux transporter gene overexpression, are gaining attention. The current study focuses on the expression alterations of drug efflux transporter genes in voriconazole (VRC)-resistant environmental A. fumigatus isolates that do not exhibit mutation in cyp51A gene.
Methods: A total of 120 soil samples were collected from agricultural fields across India and were investigated for antifungal susceptibility testing using the Clinical and Laboratory Standards Institute M38-A2 methodology. cyp51A gene sequencing and in-silico protein homology modelling was carried out. Further, expression analysis of cyp51A, cyp51B and drug efflux transporter genes mdr1, mdr4, abcA, cdr1B, mfsc, hmg1 with and without VRC exposure was conducted on azole resistant A. fumigatus isolates.
Results: A total of 56 A. fumigatus isolates were identified from 120 soil samples, out of these 8 were found to be VRC-resistant. Among them, 3 were carrying the TR46/T289A mutation in cyp51A region, 2 isolates lacking the cyp51A mutation, and 3 isolates carrying novel mutations (K67Q, L77W and L477I) in cyp51A region. However, Cyp51A homology modelling revealed that these novel mutations resulted in insignificant structural variations in the Cyp51A protein. Furthermore, gene expression analysis showed that out of 3 isolates carrying the novel mutation, 2 exhibited significant overexpression of the efflux pump gene hmg1 after exposure to VRC. While, one of the isolate showed up regulation of mfsc gene following VRC exposure. Notably, mfsc gene overexpression was also observed in 2 isolates without Cyp51A mutations after VRC exposure. In contrast, 3 VRC-resistant isolates with TR46/T289A mutations did not display significant overexpression, except for the cyp51A gene.
Conclusions: These findings suggested that VRC resistance in A. fumigatus isolates cannot be solely attributed to the cyp51A gene mutation. The overexpression of efflux pump genes appears to play a potential role in drug resistance, in addition to the cyp51A gene mutation.

Abstract Number: 5

Conference Year: 2024

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