Fungal Infections

Species name, teleomorph and common name

Trichophyton rubrum; teleomorphic clade association: Arthroderma

Two types may be distinguished: T. rubrum downy type and T. rubrum granular type

Natural habitat

Anthropophilic dermatophyte: infectious lesions (tinea); animals very rarely infected.T. rubrum is an obligate human pathogen not found in the environment.

Geography

Global.

Granular strain frequent cause of tinea corporis in South East Asia and in Aborigines living in the Northern Territory of Australia. However, since the Vietnam War, it has been spread throughout the world, especially to those countries with returning troops or to those receiving refugees, where it has often been described as a new species.

The granular represents the parent strain of the downy type; the later evolved by establishing a niche on the feet (tinea pedis) when the former was imported into Europe about 100 years ago.

Frequency

Most widely distributed dermatophyte of man.

Diseases

Tinea of the groin, glabrous skin, feet, hands, and the nails. Tinea cruris, tinea corporis, tinea pedis, tinea manuum, and onychomycosis. The scalp is very rarely infected.

Culture peculiarities

A very variable organism and many characteristics either overlap or are inconsistent. Two types may be distinguished: T. rubrum downy type and T. rubrum granular type. On Sabouraud glucose agar, growth slow to moderately rapid, texture downy, sometimes powdery. Colour white to pale pink on the surface; reverse typically wine red, sometimes brown, violet, yellow or even uncoloured. Intermediate strain between the types occur.

Antifungal resistance (intrinsic and acquired)

Ketoconazole, clotrimazole, itraconazole, fluconazole, terbinafine, naftifine, and amorolfine are in general active in vitro against T. rubrum

Biosafety level

This organism may be handled in a biosafety level 2 laboratory.

Industrial use

None

 Images

Trichophyton rubrum downy type. Cultures are generally white, suede-like to downy with characteristic deep wine-red reverse pigment.

Microscopy of a culture of T. rubrum

Direct microscopy showing T. rubrum hyphae in a skin sample.

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