Clinico-mycological and therapeutic updates on tinea corporis/cruris in the era of Trichophyton indotineae

Trichophyton indotineae (TI) has emerged as a novel dermatophyte species causing treatment recalcitrant skin infections. While the earliest reports came from India, TI has now spread to many parts of the world and is rapidly becoming a global health concern. Accurate identification of TI requires elaborate mycological investigations not in the domain of routine microbiology laboratories. Extensive, non-inflammatory and atypical presentations are commonly seen with this novel species. TI shows an alarmingly high rate of mutations in the squalene epoxidase gene leading to lowered invitro susceptibility to terbinafine. This has also translated into a lowered clinical response and requirement of a higher dose and much longer durations of treatment with the drug. Although the species remains largely susceptible to Itraconazole (ITZ), prolonged treatment durations are required to achieve cure with ITZ as well. Fluconazole and griseofulvin do not have satisfactory invitro or clinical activity. Apart from requirement of prolonged treatment durations, relapse post successful treatment is a distressing and yet unexplained consequence of this "species-shift". Use of third generation azoles and combinations of systemic antifungals is unwarranted as both have not demonstrated clear superiority over ITZ given alone, and the former is an important class of drugs for invasive mycoses.