Molecular detection of subtilisin and fungalysin genes and antifungal susceptibility of Microsporum canis from human and animal dermatophytosis

Microsporum canis is a zoonotic dermatophyte responsible for dermatophytosis in both animals and humans, whereas Arthroderma otae represents its teleomorphic state. Considering the increasing incidence of dermatophytosis, emerging antifungal resistance and limited availability of related reliable data in Iraq, this study aimed to evaluate the antifungal susceptibility patterns of Microsporum canis and to molecularly characterize selected virulence-associated genes and to assess the genetic relatedness and evolutionary relationships among the isolates. A total of 250 clinical samples were collected from dermatophyte lesions and screened, from which 57 molecularly confirmed isolates (40 M. canis and 17 A. otae) were obtained. The presence of Subtilisin (SUB1-3) and Fungalysin (MEP1-5) genes was assessed using both previously published and newly designed specific primers. Additionally, antifungal susceptibility testing of isolates using the broth microdilution method was performed against commonly used antifungal agents. The results revealed that, except for MEP2 and MEP5, all isolates of M. canis and A. otae carried SUB2, SUB3, MEP1, and MEP3, with no significant difference between human and animal isolates (p ≥ 0.05). However, SUB1 and MEP4 showed variable distribution. Antifungal susceptibility analysis revealed significant differences among tested agents (p = 0.006). Terbinafine exhibited the highest antifungal activity, whereas fluconazole exhibited the lowest, suggesting reduced susceptibility. These results demonstrate the widespread distribution of key protease enzyme-coding genes in dermatophyte isolates and their variable antifungal profiles in humans and animals. Although the present findings support the integration of molecular characterization with antifungal susceptibility testing, the presence of these genes alone does not confirm their functional role in pathogenicity; therefore, further functional and epidemiological investigations are required to clarify their significance.