Trichophyton fungus. Cultured Trichophyton megninii fungus in a petri dish. The vegetative phase of the fungus, the mycelium, has grown out from the centre. T. megninii, like other species of Trichophyton, is a dermatophyte fungus, which infects the skin, hair and nails. Such infections are often called ringworm. Various antifungal drugs are used to treat infection with Tricophyton.