Molecular strain typing of Trichophyton mentagrophytes (T. mentagrophytes var. interdigitale) using non-transcribed spacer region as a molecular marker

Molecular identification of isolates of the Trichophyton mentagrophytes complex

Background: The Trichophyton mentagrophytes complex is the second most common causal agent of dermatophytosis. It comprises five species-T. mentagrophytes, T. interdigitale, T. erinacei, T quinckeanum, and T. benhamie, as well as nine different genotypes of T. mentagrophytes / T. interdigitale-which are morphologically similar; however, their susceptibility to antifungal agents may differ. For targeted therapy and better prognosis, it is important to identify these species at a molecular level. However, since many hospitals lack molecular methods, the actual aetiology of dermatophytosis caused by this complex remains unknown. Objective: To characterize 55 anthropophilic isolates of the T. mentagrophytes complex recovered from a dermatological centre in Yucatán, Mexico. Material and methods: Fifty-five isolates of the T. mentagrophytes complex were obtained from patients with tinea capitis, tinea pedis, tinea corporis, tinea barbae, and tinea unguium. They were characterized by their colonial and microscopic morphology on Sabouraud dextrose agar (SDA) and through the sequencing of a fragment from the region ITS1-5.8S-ITS2. Results: All colonies grown on SDA were white. Forty-six isolates formed colonies with a powdery texture, while nine isolates formed colonies with a velvety texture. The micromorphological features were typical of the T. mentagrophytes complex. The molecular analysis revealed that 55 isolates were microorganisms that belonged to the T. mentagrophytes complex, that 46 formed powdery colonies representing T. mentagrophytes, and that the other nine isolates that formed velvety colonies represented T. interdigitale. The latter nine isolates were obtained from patients with tinea pedis, tinea corporis, and tinea unguium. Conclusions: The colony morphology on SDA led to the identification of 46 isolates as T. mentagrophytes and nine isolates as T. interdigitale. At a molecular level, the species identified by their morphology were identified only as T. mentagrophytes complex.

The Current Indian Epidemic of Dermatophytosis: A Study on Causative Agents and Sensitivity Patterns

Background

In the recent years, the frequency, severity, clinical characteristics, treatment response, and relapse rate of dermatophytosis have dramatically changed in India. Given the surge in dermatophytosis, we had undertaken a study to isolate and identify the common species causing dermatophyte infection and to know the in vitro efficacy of the common antifungals against them.

Materials and Methods

A total of 103 new cases that were not on any treatment for the past 3 months were included. Skin scrapings were collected for direct microscopic examination and for fungal culture in Sabouraud 4% dextrose agar (SDA) with chloramphenicol and cycloheximide slant tubes, and dermatophyte test media. Fungi were identified on the basis of their macroscopic and microscopic features with the help of lactophenol cotton blue staining and urease test. Also, the drug sensitivity of the dermatophytes was tested with the common antifungals.

Results

Of the 55 cases (53.4%) that were positive for dermatophytes in the culture, 29 showed possible contamination. Trichophyton was the predominant organism (49 cases) with T. verrucosum being the commonest species (26 cases), followed by T. rubrum (15 patients), and T. mentagrophytes (8 cases). All species of Trichophyton were found to be most sensitive to itraconazole amongst systemic antifungals and luliconazole amongst topical antifungals.

Conclusion

This study concluded that the causative agent for the dermatophytosis was changing in India and in our subset, T. verrucosum caused the maximum number of infections. Itraconazole and luliconazole had the highest sensitivity amongst systemic and topical antifungals, respectively. It also showed that terbinafine had comparatively less sensitivity to most organisms.