In vitro degradation of equine keratin by dermatophytes and other keratinophilic fungi

Keratinolytic properties of two dermatophytes (Microsporum gypseum, Trichophyton mentagrophytes) and three moulds (Scopulariopsis brevicaulis, Alternaria alternata, Geotrichum candidum) isolated from diseased equine hooves were examined to improve the understanding of pathogenic mechanisms leading to equine onychomycosis. Equine hoof horn material and skin, as well as hoof keratin and dermal keratin extracted from corresponding tissues, were used as sole carbon and nitrogen sources in five test tubes for each fungus. Within 18 days, supernatants of all tubes were repeatedly examined for keratinolytic activity by SDS-PAGE and Western blot analysis. In addition, fungal growth rates were determined to identify the preferred tissue of the individual fungi.Among the fungi examined, M. gypseum was the most keratinolytic species, followed by T. mentagrophytes and S. brevicaulis. In the concentration applied, the moulds A. alternata and G. candidum showed minimal keratinolytic activity. With respect to growth rates, M. gypseum favoured hoof horn material, S. brevicaulis and G. candidum preferred skin as a keratin source, whereas for the other two fungi no clear preference was detectable.