Trichophyton fungal culture (white patches) in a test tube. This fungus is Trichophyton soudanese, and has been spread by migration from Africa. It is a dermatophyte fungus, one that is a parasite on human skin. It causes forms of ringworm (also called tinea), where itchy, flaky patches appear on the skin. The fungus is being cultured in a medium that provides nutrients for its growth.