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Emergence of resistant dermatophytosis caused by Trichophyton indotineae: First case series in Thailand

Summary

Researchers in Thailand have identified the first cases of a new resistant fungal skin infection caused by Trichophyton indotineae. This fungus is resistant to a commonly used antifungal drug called terbinafine and causes persistent skin rashes on various body parts. The study describes five patients whose infections were finally identified through genetic testing and who responded well to alternative antifungal treatment with itraconazole. This discovery suggests the fungus is now spreading in Thailand and doctors should watch for it.

Background

Trichophyton indotineae is a terbinafine-resistant dermatophyte that was first reported in India in 2018 and has since spread globally. This organism is difficult to differentiate from other members of the Trichophyton mentagrophytes complex using conventional morphological methods. Until this report, no confirmed cases of T. indotineae infection had been documented in Thailand.

Objective

To identify and characterize cases of Trichophyton indotineae infection in Thailand by screening patients with culture results consistent with Trichophyton mentagrophytes complex using urease testing and molecular analysis. The study aimed to confirm the presence and spread of terbinafine-resistant dermatophytosis in Thailand.

Results

Five Thai patients were identified with T. indotineae infection. Two patients harbored SQLE gene mutations (Phe397Leu at positions 1191C>A and 1189T>C), and two isolates showed high MIC values >1 mg/L for terbinafine. All five isolates showed negative urease test results, which correlated with T. indotineae identification by DNA sequencing.

Conclusion

This is the first confirmed case series of T. indotineae in Thailand, indicating that terbinafine-resistant dermatophytosis has emerged in the country. The urease test may serve as a simple, inexpensive screening tool to differentiate T. indotineae from other Trichophyton mentagrophytes complex members. Itraconazole was effective as first-line treatment in most patients.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Series,
  • Source: PMID: 40547227, DOI: 10.1016/j.mmcr.2025.100713
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