# Fluconazole resistance among Candida species with special emphasis on ERG11 gene mutations among Candida tropicalis

## TL;DR

This study examines fluconazole resistance in Candida species, focusing on ERG11 gene mutations in Candida tropicalis and comparing different testing methods.

## Contribution

The study identifies ERG11 gene mutations in C. tropicalis and highlights the multifactorial nature of fluconazole resistance.

## Key findings

- 7.07% of Candida isolates were fluconazole-resistant, with C. tropicalis being the most common resistant species.
- ERG11 gene mutations A395T and C461T were detected in 6 out of 15 C. tropicalis isolates.
- Vitek-2 is recommended for AST due to its ease and cost-effectiveness, while PCR reveals additional resistance mechanisms.

## Abstract

Candidiasis, an opportunistic fungal infection, is increasingly caused by non-albicans Candida species that show reduced fluconazole susceptibility, mainly due to ERG11 overexpression. This study aimed to identify Candida species, determine fluconazole resistance using VITEK 2 and disc diffusion methods, and detect ERG11 gene mutations in Candida tropicalis.

A total of 410 clinical samples were included in this laboratory-based prospective study conducted at a tertiary care hospital in Mysuru. Fluconazole-resistant Candida species were identified using the Vitek-2 system and disc diffusion methods. The ERG11 gene of fluconazole-resistant strains of Candida tropicalis was amplified by polymerase chain reaction (PCR) and subjected to high-resolution melt (HRM) analysis to detect A395T and C461T mutations.

A total of 410 Candida species were isolated from 410 clinical isolates during the study period, with 61% (250/410) from males and 39% (160/410) from females. Among the 410 isolates tested by Vitek-2, 29 (7.07%) were resistant to fluconazole, with the majority being C. tropicalis (51.7%). Of the 15 C. tropicalis isolates tested, A395T and C461T mutations in the ERG11 gene were detected in 6 isolates. These isolates showed high minimum inhibitory concentrations (MICs) to azoles. Discrepancies between Vitek-2 and PCR findings likely reflect the multifactorial nature of fluconazole resistance and the presence of resistance mechanisms beyond the targeted ERG11 mutations.

The study concludes that antifungal susceptibility testing (AST) using Vitek-2 is a preferred method in the laboratory for identifying Candida species and performing susceptibility testing due to its ease of use and cost-effectiveness. Disc diffusion can be utilized in resource-limited settings to guide treatment, while PCR and newer molecular methods offer valuable opportunities for researching different mechanisms and mutations responsible for fluconazole resistance, a widely used antifungal for treatment and prevention.