Resistance & virulence traits in dermatophytes isolated from Mangaluru, India

Background & objectives Dermatophytes are accountable for the majority of fungal skin infections globally, affecting 20-25 per cent of the world population. Though not fatal, these infections have significant psychosocial impacts and reduce the quality of life. Prevalence of the infection varies geographically, influenced by factors like social practices, migration and climate. Understanding the pathogenicity of dermatophytosis including virulence factors and drug resistance, is necessary to identify factors that predispose recalcitrance. Methods A prospective hospital-based study was carried out in the dermatology departments of two tertiary care hospitals in Mangaluru, India from November 2018 to March 2021. We included 93 individuals of recalcitrant tinea infections, and excluded those with diabetes or those under immunosuppressive therapy. Skin scrapings from lesions were cultured, and DNA extracted for ITS sequencing. All samples were processed for antifungal susceptibility testing, and mutation analysis in squalene epoxidase gene for representative isolates and virulence factor assays. Results Of 93 clinically diagnosed individuals with dermatophytosis, dermatophytes were recovered in 70.96 per cent samples, with Trichophyton mentagrophytes complex being the most common agent. Antifungal susceptibility testing showed high MICs for fluconazole, terbinafine and itraconazole in several isolates, indicating in-vitro resistance. Mutation analysis for six isolates revealed missense mutations in the squalene epoxidase gene. Virulence activity analysis showed high enzyme production levels among isolates, contributing to their pathogenicity. Interpretation & conclusions These findings underscore the complexity of dermatophytosis and emphasize the need for persistent tracking of antifungal resistance patterns and virulence factors. Such insights are vital for developing effective treatment strategies and improving patient outcomes due to rising antifungal resistance.