Trichophyton rubrum
![](/Images/godic/202502/17/Trichophyton_rubrum_microconidia5631.jpg")
![Bottom view of a Sabouraud agar plate with a colony of Trichophyton rubrum var. rodhainii.](/Images/godic/202502/17/Trichophyton_rubrum_var._rodhaini_PHIL_4248_lores5631.jpg")
![Colonies of T. rubrum isolated from toenail (left-right): Primary isolation from scrapings on Sabouraud's dextrose agar with cycloheximide, chloramphenicol and gentamicin (14 d); Greenish colonies on Littman Oxgall agar (14 d); Restricted, red colony without pH change on Bromocresol Purple Milk Solids Glucose agar (10 d).Colonies of T. mentagrophytes (left), T. rubrum (center) and T. violaceum (right) showing differential responses on Bromocresol Purple Milk Solids Glucose agar (7 d). T. mentagrophytes shows unrestricted growth with alkaline (purple) colour change, T. rubrum shows restricted growth with no pH change, and T. violaceum produces weak growth accompanied by clearing of the milk solids and a purple colour change.](/Images/godic/202502/17/Trichophyton_rubrum_colonies_8005631.jpg")
![Three tubes of opaque purple growth medium, the left showing a cottony white colony, the middle with a small red and the right with one with a small colony surrounded by a clear halo](/Images/godic/202502/17/Mentag_rubrum_violaceum5631.jpg")
Trichophyton rubrum is a dermatophytic fungus in the phylum Ascomycota, class Euascomycetes. It is an exclusively clonal, anthropophilic saprotroph that colonizes the upper layers of dead skin, and is the most common cause of athlete's foot, fungal infection of nail, jock itch, and ringworm worldwide. Trichophyton rubrum was first described by Malmsten in 1845 and is currently considered to be a complex of species that comprises multiple, geographically patterned morphotypes, several of which have been formally described as distinct taxa, including T. raubitschekii, T. gourvilii, T. megninii and T. soudanense.