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

Summary

Researchers in Thailand have identified five patients with a difficult-to-treat fungal skin infection caused by Trichophyton indotineae, a type of dermatophyte that resists the commonly used antifungal drug terbinafine. This is the first time this resistant fungus has been detected in Thailand. The team developed a simple, inexpensive test using urease to help identify these resistant infections more easily. Patients responded well to the antifungal drug itraconazole after other treatments failed.

Background

Trichophyton indotineae is a terbinafine-resistant dermatophyte that emerged in India in 2018 and has since spread globally. This organism is difficult to differentiate from other Trichophyton mentagrophytes complex members using conventional morphological methods. No cases of T. indotineae infection had been previously reported in Thailand.

Objective

To identify and characterize Trichophyton indotineae infections in Thai patients through screening of fungal isolates with negative urease test results and confirmation by molecular analysis and squalene epoxidase gene testing.

Results

Five Thai patients were diagnosed with T. indotineae infection. Two of five isolates (40%) had SQLE gene mutations at position Phe397Leu, and two isolates showed high MIC values >1 mg/L to terbinafine. All five isolates gave negative urease test results and were confirmed by DNA sequencing. All patients had histories of drug resistance to prior antifungal treatments.

Conclusion

This is the first case series of T. indotineae infection reported in Thailand, confirming the spread of terbinafine-resistant dermatophytosis in the country. The urease test is suggested as a simple, inexpensive screening tool to help differentiate T. indotineae from other T. mentagrophytes complex members. Itraconazole was the effective treatment for these resistant infections.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Series,
  • Source: PMID: 40547227, DOI: 10.1016/j.mmcr.2025.100713
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