Green fluorescent protein (GFP) as a vital marker for pathogenic development of the dermatophyte Trichophyton mentagrophytes.

Skin infections by dermatophytes of the genus Trichophyton are widespread, but methods to investigate the molecular basis of pathogenicity are only starting to be developed. The initial stages of growth on the host can only be studied by electron microscopy, which requires fixing the tissue. This paper shows that restriction-enzyme-mediated integration (REMI) provides stable expression of the green fluorescent protein (GFP) in a clinical isolate of Trichophyton mentagrophytes. Under control of a constitutively active fungal promoter, GFP renders the hyphae fluorescent both in culture and in a recently developed model using human skin explants. Stages of infection and penetration into the skin layers were visualized by confocal microscopy. The stages of infection can thus be followed using GFP as a vital marker, and this method will also provide, for the first time, a means to follow gene expression during infection of skin by dermatophyte fungi.