Drug-resistance genes and antifungal susceptibility of Trichophyton verrucosum variants isolated from bovine skin lesions and farm environments

Abstract

• Background Trichophyton verrucosum is a zoophilic dermatophyte that causes a highly contagious disease in bovine, and can be occasionally transmitted to humans. Azoles are wildly used as antifungal drugs in bovine; they act by targeting the ergosterol biosynthesis pathway. However, recently, several cases of failure and relapse of dermatophyte infection have been reported due to gene mutations in the drug target site. In addition, subtilisin (SUB) genes play an important role in pathogenesis. However, there is limited information regarding T. verrucosum variants. This study aimed to classify T. verrucosum variants based on their antifungal susceptibility and the presence or absence of ergosterol biosynthesis (ERG) and SUB genes, isolated from animals with clinical symptoms and cattle environments (fence and water bowel) in the Republic of Korea. • Results Of 139 clinical samples and 39 environmental samples, 86 and 21 were found to be infected, respectively. The positive ratio of calves aged 1–6 months was 73.1%, which was significantly higher than that of calves aged > 6 months (55.2%). Twenty-seven T. verrucosum strains were identified and classified as T. album (n = 9), T. ochraceum (n = 6), and T. discoides (n = 12). Antifungal susceptibility testing showed that enilconazole had the lowest geometric mean antifungal activity, of 1.08, 1, and 0.94 µg/ml against T. album, T. ochraceum, and T. discoides, respectively. All strains harbored SUB6 and ERG11. The distribution of SUB5, ERG3, and ERG6 among the three variants was significantly different. • Conclusions To the best of our knowledge, this is the first report of the antifungal susceptibility and presence/absence of SUB and ERG genes in T. verrucosum variants isolated from bovine and farm environments in the Republic of Korea. This information regarding T. verrucosum variants may help prevent and manage dermatophytosis in cattle.