| Summary: | Terbinafine resistance in <i>Trichophyton</i> species has emerged and appears to be increasing. A new EUCAST susceptibility testing method and tentative ECOFFs were recently proposed for <i>Trichophyton</i>. Terbinafine resistance and target gene mutations were detected in 16 Danish isolates in 2013–2018. In this study, samples/isolates submitted for dermatophyte susceptibility testing 2019–2020 were examined. Species identification (ITS sequencing for <i>T. mentagrophytes/T. interdigitale</i> species complex (SC) isolates), EUCAST MICs and squalene epoxidase (SQLE) profiles were obtained. Sixty-three isolates from 59 patients were included. <i>T. rubrum</i> accounted for 81% and <i>T. mentagrophytes/T. interdigitale</i> SC for 19%. Approximately 60% of <i>T. rubrum</i> and <i>T. mentagrophytes/interdigitale</i> SC isolates were terbinafine non-wildtype and/or had known/novel SQLE mutations with possible implications for terbinafine MICs. All infections with terbinafine-resistant <i>T. mentagrophytes/interdigitale</i> SC isolates were caused by <i>Trichophyton indotineae</i>. Compared to 2013–2018, the number of patients with terbinafine-resistant <i>Trichophyton</i> isolates increased. For <i>T. rubrum</i>, this is partly explained by an increase in number of requests for susceptibility testing. Terbinafine-resistant <i>T. indotineae</i> was first detected in 2018, but accounted for 19% of resistance (4 of 21 patients) in 2020. In conclusion, terbinafine resistance is an emerging problem in Denmark. Population based studies are warranted and susceptibility testing is highly relevant in non-responding cases.
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