Mechanism of azole resistance in Candida glabrata isolates from India: clinical vs. induced perspectives

TL;DR

This study explores how Candida glabrata from India develops resistance to antifungal drugs, comparing clinical and lab-generated strains.

Contribution

The study reports for the first time fluconazole resistance mechanisms in Indian C. glabrata clinical isolates.

Findings

Clinical isolates showed fluconazole resistance with increased CDR1 expression and novel PDR1 mutations.

Lab-generated resistant strains exhibited ERG11 overexpression and specific mutations.

Biofilm activity contributed to resistance in one clinical isolate.

Abstract

Introduction.
Candida glabrata is a pathogenic yeast in humans, recognized for its genomic plasticity and increasing prevalence of antifungal resistance, including multidrug-resistant phenotypes, especially in the US and European countries.

Hypothesis. This study hypothesizes that the resistance mechanisms in clinically resistant strains of C. glabrata differ from laboratory-generated resistant strains.

Aim. This study aims to understand the resistance mechanism in Indian clinical isolates of C. glabrata.

Methodology. A total of 240 clinical isolates of C. glabrata were tested for antifungal susceptibility and one resistant strain was artificially synthesized in the laboratory. Both clinical and lab-generated resistant strains were analysed for antifungal resistance using methods such as phenotypic assays, real-time quantitative PCR, Fluorescence-activated cell sorting (FACS) analysis and targeted gene sequencing. Mechanisms involving drug efflux pumps, mismatch repair pathways, ergosterol biosynthesis pathway and biofilm formation were systematically studied.

Results. Among clinical isolates, one susceptible-dose dependent strain and three fluconazole-resistant strains were identified. Both clinical and lab-generated resistant strains demonstrated antifungal resistance phenotypically, with increased expression of CDR1. Targeted gene sequencing revealed novel mutations in PDR1, while mutations in MSH2 served as genotypic markers for resistance. Overexpression of ERG11 was seen in a lab-generated resistant strain where a specific mutation was identified. Biofilm activity contributed to resistance in one of the clinical strains.

Conclusion. This study reports for the first time the fluconazole resistance mechanism in C. glabrata from India. The findings underscore the diversity of resistance mechanisms among clinical and lab-generated isolates, emphasizing the need for novel antifungal therapies to address these emerging resistance profiles effectively.

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