A case of double-mutant resistant tinea indotineae

Abstract

In recent years, there has been a concerning increase in a challenging-to-treat dermatophyte lineage of the Trichophyton mentagrophytes complex, known as Trichophyton indotineae. We report the first case of resistant T. indotineae bearing a double mutation in the squalene epoxidase gene (SQLE), isolated in Italy from a 26 -year-old Nepali woman affected by a persistent tinea corporis. Topical terbinafine yielded minimal to no improvement while itraconazole provided partial relief but failed to eradicate the infection. Molecular identification through Sanger sequencing of the internal transcribed spacer region confirmed T. indotineae and sequencing of the SQLE gene revealed the presence of a double mutation (Phe397Leu/Ala448Thr) associated with antifungal resistance. Broth microdilution susceptibility testing demonstrated resistance to fluconazole, but susceptibility to itraconazole. Ultimately complete cure was achieved with prolonged high-dose itraconazole therapy.