In vitro antifungal resistance and molecular analysis of the SQLE gene in dermatophytosis: a laboratory-based study

Jegan  Charlies; Latha  Ragunathan; Kavitha  Kanniyan; Jeyakumari  Duraipandian

doi:10.18502/ijm.v18i3.21667

Jegan Charlies Department of Microbiology, Vinayaka Mission’s Medical College and Hospital, Vinayaka Mission’s Research Foundation (Deemed-to–be-University), Karaikal, Puducherry, India
Latha Ragunathan Department of Microbiology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission’s Research Foundation, (Deemed-to–be-University), Kirumampakkam, Puducherry, India
Kavitha Kanniyan Department of Microbiology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission’s Research Foundation, (Deemed-to–be-University), Kirumampakkam, Puducherry, India
Jeyakumari Duraipandian Department of Microbiology, JIPMER, Karaikal, Puducherry, India

DOI: https://doi.org/10.18502/ijm.v18i3.21667

Keywords: Antifungal resistance; Gene expression; Minimum inhibitory concentration; Polymerase chain reaction; Squalene epoxidase

Abstract

Background and Objectives: Dermatophytosis is a common superficial fungal infection that affects the keratinised tissues. This study examines the antifungal resistance mechanisms and molecular detection of squalene epoxidase gene alterations in clinical isolates from patients.

Materials and Methods: A cross-sectional study conducted from January 2019 to December 2020 included 110 clinically suspected dermatophytosis specimens. Microscopy, culture, CLSI M38-A2 broth microdilution testing, and PCR-based ITS and SQLE (520 bp) amplification were performed. MIC50, MIC90, geometric mean, and ranges were analysed using SPSS version 19 with P < 0.05.

Results: A total of 110 suspected cases were evaluated, with 78 (70.9%) males. KOH positivity reached 100%, while culture positivity was 47.3% (52/110). Trichophyton rubrum accounted for 38.5% isolates. Fluconazole MICs were ≥64 µg/mL. 39/52 isolates showed terbinafine resistance, with 23 expressing the 520 bp SQLE gene.

Conclusion: Terbinafine and caspofungin showed consistent in vitro activity, while fluconazole showed limited activity. Routine susceptibility testing guides drug selection, improves treatment outcomes, and supports rational management of resistant dermatophytosis cases.