Trichophyton rubrum

Author: Prof. Dr. med. Peter Altmeyer

Co-Autors: Cert. ing. Christoph Kreps, Dr. med. Jelena Krochmann

All authors of this article

Last updated on: 29.10.2020

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History
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Sabouroud, 1911

Definition
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Anthropophilic dermatophyte.

Trichophyton rubrum is a skin fungus (anthropophilic dermatophyte) which colonises the horny substance in humans. It can cause numerous dermatophytoses in humans, and the pathogen is particularly common in the foot and nail fungus and the tinea inguinalis. Like all dermatophytes Trichophyton rubrum feeds on keratin. It is transmitted from person to person by direct or indirect contact. Transmission from humans to animals is also rare [1] Teleomorphism, i.e. the sexual stage of T. rubrum, is still unknown.

General definition
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Very good adaptation to humans and high affinity to nail keratin. Transmission occurs, among other things, from person to person (patients with persistent nail mycoses are a constant reservoir of the pathogen), through laundry, bath mats, in saunas, bathing facilities or shower rooms.

Occurrence/Epidemiology
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Worldwide spread. By far the most common human pathogenic dermatophyte in Europe (70-80%). Most frequent pathogen of nail and foot mycoses. Men are significantly more frequently affected than women.

Clinical picture
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Local infections of the hands (especially palm and ulnar edge of the hand; less frequently on the fingers or back of the hand), feet, nails (often associated with leukonychia ) and groins. S.u. tinea, tinea corporis, tinea barbae, tinea manuum, tinea pedum, tinea unguium, tinea granulomatosa follicularis et nodularis cruris. In the case of infestation of the arms, sharply defined, reddened, scaly round foci are usually impressive. In manifestations of the legs, flat, reddened, scaly plaques usually develop. Only very rarely infections of the capillitium are observed, see below. Tinea capitis superficialis. Rarely and almost exclusively in men tinea inguinalis. Occasionally causes systemic infections. Frequently chronic recurrent courses of the disease. In individual cases occurrence of Id reactions.

Microscopy
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  • In the native preparation, T. rubrum shows up in the form of a widely branched mycelium in case of skin diseases, and as spore chains in case of nail fungus.
  • Long, thin hyphae, no spiral hyphae. Very rare occurrence of chlamydospores.
  • Macroconidia: usually absent (exception: granular variants), long and smooth-walled, sausage- to cigar-shaped, strongly septated, rounded at the poles, length: 15-40 μm, width: 4-6 μm, 3-8 chambers.
  • Microconidia: are very rare, unicellular, pear-shaped, acladium-shaped, arranged at the hyphae staggered (in acladium form), length: 3-5 μm, width: 2-3 μm.

Diagnosis
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Sabouraud dextrose agar: Formation of white, cotton wool-like, hat-shaped colonies with radial folding, which become greenish or red to violet in the fringe area; in woodlight diagnosis it shows no fluorescence. Underside of the culture wine-red.

Mycosel medium: Formation of an initially yellow, later red rim. Underside of the culture wine-red.

Creamy agar: cream-coloured culture with central raised area and broad, flat rim.

For a reliable differentiation of Trichophyton rubrum and Trichophyton interdigitale, special culture media (e.g. potato glucose agar or urea agar) may be additionally required for the detection of urea cleavage of Trichophyton interdigitale.

Note(s)
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Known and analysed type I allergens in Trichophyton rubrum

  • Tri r 2 Putative secreted alkaline protease Alp1
  • Tri r 4 Serine protease

Literature
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  1. Ellis D (2000) Epidemiology: surveillance of fungal infections. Med Mycol 38: S173-182
  2. Kick G, Korting HC (2001) The definition of Trichophyton rubrum syndrome. Mycoses 44: 167-171
  3. Lacroix C (2002) Tinea pedis in European marathon runners. J Eur Acad Dermatol Venereol 16: 139-142
  4. Mungan D et al (2001) Trichophyton sensitivity in allergic and nonallergic asthma. Allergy 56: 558-562
  5. Seebacher C et al (2007) Onychomycosis. J Dtsch Dermatol Ges 5: 61-66
  6. Yazdanparast A et al (2003) Molecular strain typing of Trichophyton rubrum indicates multiple strain involvement in onychomycosis. Br J Dermatol 148: 51-54

Disclaimer

Please ask your physician for a reliable diagnosis. This website is only meant as a reference.