致病：主要侵犯皮肤、指甲（趾甲）和毛发，引起体股癣、手足癣和甲癣。【常见皮肤癣菌】很少侵犯毛发。

分型：

Trichophyton rubrum?granular strain

On Sabouraud’s dextrose agar, colonies are flat to slightly raised, white to cream, suede-like with a pinkish-red reverse. Microscopically, most cultures have numerous clavate to pyriform microconidia and moderate numbers of smooth, thin walled multiseptate, slender cylindrical macroconidia. Older cultures may show numerous chlamydospores with few clavate to pyriform microconidia.

ultures of?Trichophyton rubrum?granular strain.

Macroconidia and microconidia of?T. rubrum?granular type.

Kaminski’s Dermatophyte Identification Scheme:

Littman Oxgall Agar (Difco):?Raised, greyish, suede-like colonies with some radial folding and a greenish-yellow diffusible pigment.

Lactritmel Agar (Mycopathologia 91:57-59, 1985):?Flat, white to rose pink, suede-like to granular colonies with a pinkish to wine-red reverse. Numerous broad clavate to pyriform microconidia and moderate numbers of smooth, thin-walled, slender cylindrical macroconidia are present. A few chlamydospores may be present in older cultures.

Sabouraud’s Dextrose Agar with 5% NaCl:?A very stunted, heaped and folded, glabrous, cream thallus, later developing a dark red central spot. Reverse is a brownish-yellow colour.

1% Peptone Agar:?Flat, white to cream, glabrous to suede-like colony with no reverse pigment.

Hydrolysis of Urea:?Positive at 7 days

Vitamin Free agar (Difco Trichophyton Agar No.1):?Good growth indicating no special nutritional requirements. Culture shows white to cream suede-like colonies with a pinkish-red to wine-red reverse.

Hair Perforation Test (“in vitro”): Positive.

The above morphological and cultural characteristics are typical of?Trichophyton rubrum?granular type. Two other strains or varieties of the?T. rubrum?granular type have been recognized.

1. T. rubrumvar. rhodainii

Microscopically similar to granular type except many of the thin-walled macroconidia often show terminal appendages. Colonies are characteristically hyperpigmented with a violet to red-violet, heaped and folded, glabrous surface and a deep red-violet reverse

2. T. rubrum?African type

Microscopically similar to granular strains, except the macroconidia usually have terminal appendages. Colonies are powdery and will produce characteristic wine-red reverse pigmentation on pigment stimulating media. May or may not show characteristic red reverse pigment on primary isolation media.

Clinical significance:

Trichophyton rubrum?granular strain is a frequent cause of tinea corporis in South East Asia and in Aborigines living in the Northern Territory of Australia. However, since the Vietman 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 strain of?T. rubrum?represents the parent strain of?T. rubrum?downy type; the later evolved by establishing a niche in feet (tinea pedis) when the former was imported into Europe around the turn of the century. It should be stressed that intermediate strains between the two types do occur and that many culture and morphological characteristics overlap. Invaded hairs show ectothrix or endothrix infection but do not fluoresce under Wood’s ultra-violet light.

Mycosis:?Dermatophytosis

Further reading:

Rebell, G., and D. Taplin. 1970. The Dermatophytes. 2nd. revised edition. University of Miami Press, Coral Gables, Florida. USA.

Rippon, J.W. 1988. Medical Mycology. 3rd Edition. W.B. Saunders Co., Philadelphia, USA.

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Trichophyton rubrum?downy strain

On Sabouraud’s dextrose agar, colonies are flat to slightly raised, white to cream, suede-like to downy, with a yellow-brown to wine-red reverse. Most cultures show scanty to moderate numbers of slender clavate to pyriform microconidia. Macroconidia are usually absent, however closterospore-like projections may be present in some mounts. Note: on primary isolation some cultures may lack reverse pigmentation and fail to produce microconidia. These will need to be subcultured onto media like Lactritmel agar or potato dextrose agar which stimulate pigmentation and sporulation. If sporulation still fails subculture the fungus onto Difco Trichophyton Agar No.1.? RG-2 organism.

Culture of?Trichophtyon rubrum?showing wine-red reverse pigment.

Typical slender clavate microconidia of?T. rubrum?downy type

Kaminski’s Dermatophyte Identification Scheme:

Littman Oxgall Agar (Difco):?Raised, greyish-white, suede-like to downy colony with no reverse pigment. Some cultures may have showed a faint greenish-yellow diffusible pigment.

Lactritmel Agar (Mycopathologia 91:57-59, 1985):?Flat, white, downy colonies with a deep wine-red reverse pigment. Microscopically, cultures show the typical downy type morphology of pyriform to slender clavate microconidia described above.

Sabouraud’s Dextrose Agar with 5% NaCl:?Very stunted, white downy colony with a pale yellow-brown reverse pigment.

1% Peptone Agar:?Flat, white to cream, downy colony often with a raised centre. No reverse pigment produced.

Hydrolysis of Urea:?Negative at 7 days.

Vitamin Free Agar (Difco Trichophyton Agar No.1):?Good growth indicating no special vitamin requirements. Cultures are flat, white to cream, suede-like to downy with a deep wine-red reverse pigment.

Hair Perforation Test (“in vitro”):?Negative at 28 days.

The above morphological and cultural characteristics are typical of?Trichophyton rubrum?downy type. Seven other strains or varieties of the?T. rubrum?downy type have been recognized and are listed below.

1. T. rubrum?“Y” variant

Microscopically similar to downy type. Yellow reverse pigment produced on 1% peptone agar, however characteristic red reverse pigment is produced on Sabouraud’s dextrose agar and on pigment stimulating media like Lactritmel and Trichophyton No.1 agars. May or may not show pigmentation on primary isolation media. Basically, these strains produce both yellow and red pigments.

2.?T. rubrum?var. flava

Microscopically similar to downy type. Yellow reverse pigment is produced on 1% peptone agar and on Sabouraud’s dextrose agar. Some red reverse pigment may be produced on pigment enhancing media like Lactritmel agar, but never on Sabouraud’s dextrose agar. These strains normally produce only yellow pigment.

3.?T. rubrum?”P” variant

Microscopically similar to downy type. Purple reverse pigment produced on 1% Peptone agar, however characteristic red reverse pigment is also produced on Lactritmel agar and on other pigment stimulating.

4.?T. rubrum?melanoid type

Microscopically similar to downy type. A diffusible brown, melanoid pigment is present on all media, especially 1% peptone agar. Characteristic red reverse pigment, although often discoloured by the presence of the diffusable melanoid pigment is also produced on Lactritmel agar and other pigment stimulating media.

* Note 1% peptone agar is the key medium for distinguishing the above types of T. rubrum.

5.?T. rubrum?hyperpigmented type

Microscopically similar to downy type. All cultures show a violet to red-violet glabrous surface with radial furrows and a deep violet to red-violet reverse.

6.?T. rubrum?colourless variant

Microscopically similar to downy type. No reverse pigment is produced on any media.

7.?T. rubrum?dysgonic type

Microscopically restricted to distorted hyphae. All media show tiny slow growing colonies which are usually hyperpigmented. Primary isolates of this type are often confused with?Trichophyton violaceum.?These strains usually revert to the typical downy type following several sub-cultures.

Clinical significance:

Trichophyton rubrum?is an anthropophilic fungus which has become the most widely distributed dermatophyte of man. It frequently causes chronic infections of skin, nails and rarely scalp. Granulomatous lesions may sometimes occur. Infected hairs do not fluoresce under Wood’s ultraviolet light, and microscopically may show endothrix or ectothrix type of invasion. Key features include culture characteristics, microscopic morphology and failure to perforate hair “in vitro”.

Mycosis:?Dermatophytosis

Further reading:

Rebell, G., and D. Taplin. 1970. The Dermatophytes. 2nd. revised edition. University of Miami Press, Coral Gables, Florida. USA.

Rippon, J.W. 1988. Medical Mycology. 3rd Edition. W.B. Saunders Co., Philadelphia, USA.

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