Amplified fragment length polymorphism genotyping of Trichophyton indotineae indicates possible zoonotic transmission

The anthropophilic dermatophyte Trichophyton interdigitale and its counterpart T. mentagrophytes are phylogenetically closely related species. In India, the most common endemic dermatophyte species belongs to the T. indotineae. The internal transcribed spacer genotype VIII within this species complex was recently renamed as T. indotineae based on its rapid emergence in India and its elevated virulence and terbinafine resistance. While humans are considered a source of T. interdigitale infection, animals are considered a source of T. mentagrophytes. For T. indotineae it is not known whether infections occur anthropophilic or zoonotic, as there is very little data on its origin and transmission. Additionally, the environmental source of T. indotineae is unknown. In the current study, we have performed the molecular typing method amplified fragment length polymorphism on 24 T. indotineae isolates to determine the genetic diversity among animal and human origin isolates and compare it to related species. Additionally, we performed antifungal susceptibility testing by standard micro broth dilution methods against common antifungals. In contrast to the T. interdigitale which showed significant genetic variability between isolates from different cities, T. indotineae isolates demonstrate minimal genetic variability, also between samples from animals and humans, highlighting the possibility of zoonotic transmission of this virulent dermatophyte. Reduced susceptibility was found for terbinafine and griseofulvin.