Molecular and physiological analysis of the T. mentagrophytes / T. interdigitale species complex using a global set of strains
A severe outbreak of highly virulent and multi-resistant dermatophytosis is ongoing in India. There is a debate about the correct identification of the etiologic agent: Trichophyton mentagrophytes or T. interdigitale. In order to distinguish the species borderlines, a taxonomic study was undertaken combining molecular, morphological, and physiological characteristics as classification evidence. The molecular characteristics show that T. mentagrophytes s. str., Trichophyton indotineae and T. interdigitale s. str. can be distinguished by sequences of the HMG gene. Besides, the entities can be separated in a multilocus analysis using tanglegrams. For morphological characteristics, the colony pigmentation of T. mentagrophytes and T. interdigitale is similar, but Trichophyton indotineae is different. Physiological studies showed that T. interdigitale and T. mentagrophytes strains had high urease, keratinase and lipophilic activities. Conversely, Trichophyton indotineae strains tended to have lower urease, keratinase and lipophilic activity. From these preliminary data it might be concluded that Trichophyton indotineae represents a separate species. Since it is a serious public health problem, it will be important to establish the origin of the disease, either zoonotic or due to widespread misuse of antifungal creams.