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

Summary

Researchers in Thailand identified five patients with a new type of fungal skin infection caused by Trichophyton indotineae, a species that resists the common antifungal drug terbinafine. These infections appeared as rashes on various parts of the body and required treatment with alternative medications like itraconazole. The findings represent the first confirmed cases in Thailand and suggest this resistant fungus may be spreading globally. The study also showed that a simple urease test could help doctors identify this resistant strain quickly without waiting for complex genetic testing.

Background

Trichophyton indotineae is a terbinafine-resistant dermatophyte that was first reported in India in 2018 and subsequently identified in Japan and other countries. This species has not been previously reported in Thailand. The emergence of antifungal-resistant dermatophytes represents a significant clinical challenge worldwide.

Objective

To identify and characterize Trichophyton indotineae infections in Thai patients through screening of culture isolates with Trichophyton mentagrophytes complex morphology using urease testing and molecular analysis.

Results

Five Thai patients were identified with Trichophyton indotineae infection. Two of the five isolates (40%) showed SQLE gene mutations at position Phe397Leu. Two isolates had elevated terbinafine MIC values greater than 1 mg/L. All five isolates tested negative on the urease test, which helped differentiate them from other Trichophyton mentagrophytes complex members.

Conclusion

This represents the first confirmed case series of Trichophyton indotineae in Thailand. The urease test proved useful as a simple screening tool for identifying this resistant species, and itraconazole was effective as a treatment option for these patients. Further epidemiological studies with larger sample sizes are needed to determine the actual prevalence in Thailand.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Series,
  • Source: PMID: 40547227, DOI: 10.1016/j.mmcr.2025.100713
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