Modeling dermatophytosis: Guinea pig skin explants represent a highly suitable model to study Trichophyton benhamiae infections.

Dermatophyte infections are a growing health concern worldwide with increasing patient numbers, especially in children. However, detailed knowledge about infection mechanisms and virulence factors are scarce. This study aimed to establish an infection model based on guinea pig skin explants mimicking the in vivo situation as closely as possible to survey the pathogenesis of dermatophytoses. A fundamental prerequisite was the detailed description of native guinea pig skin and its morphological changes during tissue culture because comprehensive data on guinea pig skin characteristics were not available. Skin explants were harvested from healthy, adult guinea pigs and transferred to cell culture inserts. One group was inoculated with defined suspensions of colony-forming units of zoonotic Trichophyton benhamiae isolates; others served as controls to assess the tissue viability during the 10-day culture. Samples were taken on days 3, 5, 7 and 10 and processed for histological and immunohistochemical analysis. Standard tissue culture conditions provoked acantholysis and regional orthokeratotic alterations. The reduced desquamation caused hyperkeratosis paralleled by hypogranulosis or regional hyperplasia. During T. benhamiae infection, keratinocyte proliferation came to a complete halt on day 5 whereas the number of terminal deoxynucleotidyl transferase dUTP nick end labeling assay-positive cells increased moderately up to day 7. Hyphae grew massively into the skin explants causing strong keratinolysis and tricholysis. By the end of the culture, complete disintegration of the basement membrane and dermal tissue was observed. A realistic and reliable skin infection model was established to study dermatophytoses in general and cutaneous T. benhamiae infections in particular.