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Trichophyton indotineae Infection, São Paulo, Brazil, 2024

Summary

A businessman from São Paulo, Brazil contracted a difficult-to-treat fungal skin infection caused by Trichophyton indotineae, which is resistant to the common antifungal drug terbinafine. After terbinafine failed to help over 9 weeks, doctors switched him to itraconazole, which worked well after 8 weeks. Genetic testing showed his fungal strain had a specific resistance mutation and was most similar to a strain from Germany, suggesting he may have caught it while traveling in Europe.

Background

Trichophyton indotineae is an anthropophilic fungus that is frequently terbinafine-resistant and causes recalcitrant dermatophytosis. It has become endemic in South Asia with cases documented across 6 continents, and possible local transmission has been reported in the United States.

Objective

This case report documents a terbinafine-resistant T. indotineae infection in a previously healthy businessman from São Paulo, Brazil, and characterizes the isolate’s genomic features and drug resistance mechanisms.

Results

The isolate contained a terbinafine resistance-conferring SQLE F397L mutation with high MICs against terbinafine (>4 mg/L) and fluconazole (32 mg/L), but strong activity against itraconazole (0.016 mg/L) and voriconazole (0.125 mg/L). Genomic analysis showed the isolate was most similar to a terbinafine-resistant isolate from Germany collected in 2022, both sharing the F397L mutation.

Conclusion

This case highlights the importance of clinician vigilance for T. indotineae in travelers and those with difficult-to-treat tinea, enhanced laboratory capacity for species identification and genomic epidemiology, and the need for prolonged itraconazole therapy to prevent spread of antimicrobial-resistant pathogens.
  • Published in:Emerging Infectious Diseases,
  • Study Type:Case Report,
  • Source: 10.3201/eid3105.250048; PMID: 40305410
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