''Trichophyton'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

, which includes the

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

varieties that cause tinea, including

athlete's foot Athlete's foot, known medically as ''tinea pedis'', is a common skin infection of the feet caused by a fungus. Signs and symptoms often include itching, scaling, cracking and redness. In rare cases the skin may blister. Athlete's foot fungus ...

ringworm Dermatophytosis, also known as tinea and ringworm, is a mycosis, fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the a ...

, jock itch, and similar infections of the nail, beard, skin and scalp. Trichophyton fungi are

mold A mold () or mould () is one of the structures that certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal ...

s characterized by the development of both smooth-walled macro- and microconidia.

Macroconidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...

are mostly borne laterally directly on the hyphae or on short pedicels, and are thin- or thick-walled,

clavate This glossary of entomology describes terms used in the formal study of insect species by entomology, entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebr ...

fusiform Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...

, and range from 4 to 8 by 8 to 50 μm in size. Macroconidia are few or absent in many species. Microconidia are spherical, pyriform to clavate or of irregular shape, and range from 2 to 3 by 2 to 4 μm in size.

Species and their habitat preference

According to current classification, the genus includes anthropophilic and zoophilic species. Anthropophilic fungi prefer to infect humans. Zoophilic fungi prefer to infect animals other than humans. Humans and other animals are

natural reservoir In Infection, infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally li ...

Mating and meiosis

''Trichophyton mentagrophytes'' (Family Arthrodermataceae, Genus Trichophyton) is capable of both

mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. '' Copulation'' is the union of the sex organs of two sexually repr ...

and

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

Effect on humans

The anthropophilic varieties cause forms of

dermatophytosis Dermatophytosis, also known as tinea and ringworm, is a fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area aff ...

, that is, fungal infection of the skin. They are keratinophilic: they feed on the

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...

in nails, hair, and dead skin. ''Trichophyton concentricum'' causes "Malabar itch", a skin infection consisting of an eruption of a number of concentric rings of overlapping scales forming papulosquamous patches. ''Trichophyton rubrum'' and ''Trichophyton interdigitale'' cause athlete's foot (tinea pedis), toenail fungal infections (a.k.a. tinea unguium, a.k.a. onychomycosis), crotch itch (a.k.a. tinea cruris), and

(a misnomer, as there is no worm involved; it is also known as tinea corporis). ''Trichophyton schoenleinii'' cause favus (tinea capitis),''Trichophyton mentagrophytes var. mentagrophytes'' and ''Trichophyton verrucosum'' cause kerion (violent reaction results from infection with an animal dermatophytes). Fungal folliculitis is a rare hair follicle infection induced overwhelmingly by ''Trichophyton'', which can be spread

zoonotic A zoonosis (; plural zoonoses) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a virus, bacterium, parasite, fungi, or prion) that can jump from a non-human vertebrate to a human. When h ...

ally. The fungi can easily spread to other areas of the body as well and to the host's home environs (socks, shoes, clothes, showers, bathtubs, counters, floors, carpets, etc.). They can be transmitted by direct contact, by contact with infested particles (of dead skin, nails, hair) shed by the host, and by contact with the fungi's

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s. These fungi thrive in warm moist dark environments, such as in the dead upper layers of skin between the toes of a sweaty foot inside a tightly enclosed shoe, or in dead skin particles on the wet floor of a communal (shared) shower. Their spores are extremely difficult to eliminate, and spread everywhere. When the

hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

of the fungi burrow into the skin and release enzymes to digest keratin, they may irritate nerve endings and cause the host to

itch An itch (also known as pruritus) is a sensation that causes a strong desire or reflex to scratch. Itches have resisted many attempts to be classified as any one type of sensory experience. Itches have many similarities to pain, and while both ...

, which may elicit the scratch reflex, which directs the host to scratch. Scratching directly transfers fungi and dead skin particles that are infested with the fungi to the fingers and under the finger nails. From there they can be transmitted to other parts of the host's body when the host touches or scratches those. Scratching also damages skin layers, making it easier for the fungi to spread at the site of the infection. If the fungi and infested debris are not washed from the fingers and fingernails soon enough, the fungi can also infect the skin of the fingers ( tinea manuum), and burrow underneath and into the material of the fingernails (

tinea unguium Dermatophytosis, also known as tinea and ringworm, is a fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area aff ...

). If left untreated, the fungi continue to grow and spread.

Treatments

A variety of zoophilic and anthropophilic dermatophyte treatments have varying levels of success based on species type. Treatments may take up to six months.

References

External links