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Recalcitrant dermatophytosis due to Trichophyton indotineae: A case series from Sarawak, Malaysia

Summary

Three patients in Malaysia had persistent skin fungal infections caused by Trichophyton indotineae that did not respond to standard antifungal treatments. Genetic testing revealed these fungal strains carried a specific mutation making them resistant to terbinafine, the typical first-line treatment. While azole-based antifungals showed variable effectiveness depending on the specific drug and dose used, one patient achieved complete cure with voriconazole therapy. The study highlights the growing problem of drug-resistant fungal infections and the importance of targeted treatment based on laboratory testing.

Background

Trichophyton indotineae is an emerging etiologic agent of dermatophytosis that is often associated with terbinafine resistance. The pathogen comprises 15-93% of dermatophyte isolates globally and has spread primarily through human travel and immigration. Resistance rates to terbinafine in T. indotineae isolates range from 19-71% across previous studies.

Objective

This study aimed to characterize T. indotineae infections in Sarawak, Malaysia through mycological, genomic, and clinical analyses. The authors sought to provide insights into recalcitrant dermatophytosis cases and address the lack of reliable treatment guidelines and limited local data for this emerging pathogen.

Results

All three isolates were confirmed as T. indotineae and carried the L393S mutation in the SQLE gene associated with high terbinafine MICs. Azole susceptibilities were variable. Patient F79/24 achieved complete clinical cure after 12 weeks of voriconazole therapy with the lowest voriconazole MIC of 0.25 μg/mL, while patients F76/24 and F85/24 showed partial responses.

Conclusion

T. indotineae is confirmed as a causative agent of recalcitrant dermatophytosis in Sarawak, Malaysia. L393S mutation in SQLE confers terbinafine resistance while azole susceptibilities are variable, contributing to treatment complexity. Integration of molecular surveillance and robust antifungal stewardship is crucial to address the threat of antifungal-resistant T. indotineae infections.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Series,
  • Source: PMID: 41090058, DOI: 10.1016/j.mmcr.2025.100740
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