Evaluation of the DermaGenius® Resistance Multiplex Real-Time PCR assay for rapid identification and detection of terbinafine resistant <i>Trichophyton mentagrophytes</i> and <i>Trichophyton rubrum</i> species complex

Terbinafine resistance in Trichophyton species has been increasingly reported worldwide, resulting in recalcitrant and difficult-to-treat dermatophytosis. However, resistance detection is not routinely implemented in diagnostic laboratories, as conventional methods are time-consuming, technically demanding, and require specialized equipment. In this study, we evaluated the performance of the DermaGenius® Resistance real-time PCR assay for the detection of Trichophyton isolates harbouring mutations in squalene epoxidase gene (SQLE) associated with terbinafine resistance, in comparison with conventional diagnostic approaches. Thirty clinical Trichophyton isolates with known terbinafine susceptibility profiles were included. All isolates were analyzed using the DermaGenius® Resistance real-time PCR assay and standard methods, including internal transcribed spacer (ITS), SQLE gene Sanger sequencing, and antifungal susceptibility testing to terbinafine using EUCAST microdilution and gradient diffusion strip methods. The DermaGenius® Resistance assay identified 20 T. interdigitale/mentagrophytes species complex isolates, of which 11 harboured wild-type SQLE and nine mutant SQLE. It also identified 10 T. rubrum/soudanense species complex isolates, including eight with wild-type SQLE and two with mutant SQLE. With regard to terbinafine susceptibility testing using both techniques, categorical agreement (CA), based on classification into 'wild-type' (WT) and 'non-wild-type' (NWT) using ECOFF, was 100% for T. indotineae and T. rubrum. No discrepancies were observed between the two methods in the WT/NWT classification. The DermaGenius® Resistance real-time PCR assay provides a rapid and reliable tool for the detection of terbinafine resistance in clinically relevant Trichophyton species. This assay represents a practical alternative to conventional methods and may enable earlier identification of resistant strains, thereby improving patient management.