Terbinafine Resistance in Trichophyton Strains Isolated from Humans and Animals: A Retrospective Cohort Study in Italy, 2016 to May 2024

<b>Background:</b> In recent decades, globalization and international migration have increased the spread of infectious agents, including dermatophytes. Although considered minor infections, dermatophytoses are highly contagious, and they significantly reduce the quality of life, inducing itching, burning, sleep disturbances, and even depressive states. Moreover, the increasing resistance to antifungals threats the public health and burdens the costs for the healthcare system. <b>Methods:</b> DermaGenius^® Resistance Multiplex real-time PCR assay allowed to analyze the terbinafine susceptibility/resistance of 172 <i>Trichophyton</i> strains, which were isolated from human and animal samples collected from 2016 to May 2024 and previously identified by Sanger sequencing. <b>Results:</b> All the 11 animal strains belonged to the <i>T. interdigitale</i>/<i>T. mentagrophytes</i> complex and tested terbinafine sensitive. Out of 161 human strains, 9 (5.6%) showed terbinafine resistance and 7 (4.3%) were identified as <i>T. indotineae</i>. <b>Conclusions:</b> This study provides preliminary data about behavior toward antifungals in animals and finalizes the scientific information currently available about human strains, highlighting the importance of the One Health concept. Moreover, it supports the relevant role of <i>T. indotineae</i> as an emerging dermatophyte with high proportion of terbinafine resistance.