Trichophyton is a genus of fungi that (along with Epidermophyton and Microsporum) belongs to the group known as dermatophytes. This group of closely related fungi can invade keratinized tissue like skin, nails, and hair and produce an infection. Most infections are superficial and are limited to non-living tissues such as the topmost layers of the skin, but they can develop into deeper invasive diseases in immunocompromised hosts
There are about 20 species of Trichophyton. Although the genus is cosmopolitan, only T. rubrum, T. mentagrophytes, and T. tonsurans have true worldwide distribution. The distribution of other Trichophyton species is limited. They can be divided into anthropophilic, zoophilic, and geophilic species based on their primary habitat associations.
Anthropophilic species are mostly associated with humans and seldom infect other animals. On the other hand, zoophilic species usually infect animals but may occasionally infect humans. Geophilic species exist in the soil and may cause human and animal infections.
Trichophyton is transmitted through its spores and through direct or indirect contact with infected hosts. It can be transmitted between humans, and from animals to humans and vice versa. Dermatophytosis caused by Trichophyton can be contracted through contact with infected humans or animals or with contaminated objects, such as towels, bedding, manicure appliances, and hairbrushes. Furthermore, Trichophyton related skin conditions are frequently spread in areas such as pools, spas, locker rooms, and shared shower facilities. Maintenance of proper hygiene limits the spread of Trichophyton.
- Trichophyton rubrum is an anthropophilic fungus that has become the most widely distributed dermatophyte of humans. It frequently causes chronic infections of the skin, nails, and rarely the scalp. It is by far the most frequently isolated species in toenail onychomycosis (>90%).
- Trichophyton interdigitale is an anthropophilic fungus that is a common cause of tinea pedis, particularly the vesicular type, tinea corporis, and sometimes superficial nail plate invasion in humans. It is not known to invade hair in vivo. Distribution is worldwide. This species may be regarded as a clonal offshoot of the zoophilic T. mentagrophytes
- Trichophyton mentagrophytes is a zoophilic fungus with a worldwide distribution and a wide range of animal hosts including mice, guinea pigs, cats, horses, sheep, and rabbits. Produces inflammatory skin or scalp lesions in humans, particularly in rural workers. Kerion of the scalp and beard may occur.
- Trichophyton schoenleinii is an anthropophilic fungus causing favus in humans. Favus is a chronic, scarring form of tinea capitis characterized by saucer-shaped crusted lesions or scutula and permanent hair loss.
- Trichophyton violaceum is an anthropophilic fungus causing inflammatory or chronic non-inflammatory finely scaling lesions of skin, nails, beard, and scalp, producing the so-called “black dot” tinea capitis.
- Trichophyton tonsurans is an anthropophilic fungus with a worldwide distribution that causes inflammatory or chronic non-inflammatory finely scaling lesions of skin, nails, and scalp.
