TRICHOPHYTON

SPECIES

MICROSCOPIC APPEARANCE

Hyphae septate, hyaline. Conidiophores little differentiated from vegetative hyphae; microconidia (microaleurioconidia) unicellular, round, pyriform or "club-shaped", solitary or in "grape-like" clusters. Macroconidia (macroaleurioconidia) pluricellular, cylindrical, "club-shaped" or "cigar-shaped", "smooth-walled", often absent; arthroconidia and chlamydospores sometimes present. Several species are typically sterile, but may be induced to form conidia on appropriate media.

MACROSCOPIC APPEARANCE

Surface: Texture glabrous to downy; white, yellowish, beige, or red violet on surface.
Reverse: Pale, yellowish, brown or red-brown.
Growth Rate: Moderately rapid to slow growth.

DISTINGUISHING FEATURES

From a taxonomic point of view, Trichophyton is distinguished from Microsporum by its macroconidia with smooth walls. Not withstanding this, for the identification of most species it is especially important to examine the morphology of the microconidia. In the species which are normally sterile in culture, the appearance of the colony, certain physiological tests, are sometimes the type of lesion will prove useful in identification.

SPECIES Growth Texture Color
(surface/reverse)
Micro-
conidia
Macro-
conidia
Hair perforation Urease Growth factor requirement
T. ajelloi Moderately rapid Powdery, velvety Beige, orange/yellowish, blue-black pigment Pyriform,
absent or rare
Fusiform,
thick walled,
numerous

Positive Positive None
T. concentricum Very slow Glabrous, waxy White,
brown/white,
brown

Absent Absent Negative N/A None or thiamine
T. equinum Moderately rapid Downy White,
yellowish/yellow, red-brown
Pyriform,
numerous
Club-shaped, absent or rare Positive Positive Nicotinic acid
T. megninii Moderately rapid Downy
Suede-Like
Pale pink/red Pyriform,
club-shaped,
numerous

Pencil-shaped/ Cylindrical, absent or +/- numerous Variable

Positive in broth

Negative in agar

Histidine
T. mentagrophytes Moderately rapid Velvety,
powdery
White/yellowish,
brown,
red-brown

Pyriform,
round,
numerous or rare

Club-shaped,
absent or numerous
Positive Positive None
T. rubrum Slow to moderately rapid Downy, powdery White,
pale pink/red,
yellowish,
brown


Club-shaped,
pyriform,
+/- numerous

Cylindrical,
absent or +/- numerous
Negative Negative None
T. schoenleinii Very slow Glabrous Cream/cream Absent Absent Negative N/A None
T. soudanense Slow Felty/Velvety Yellowish,
rusty/yellowish,
rusty

Pyriform,
ovoid,
rare or absent

Occasional Negative Variable Variable
T. terrestre Moderately rapid Powdery to granular Cream,
yellowish/yellowish
Club-shaped,
numerous
Cylindrical,
+/- numerous
Positive Positive None
T. tonsurans Moderately Fast Powdery,
felty
White, yellow,
brown/brown,
red-brown

Club-shaped,
balloon,
numerous

Club-shaped,
sinuous,
absent or rare

Negative Positive Thiamine
T. verrucosum Very slow Glabrous White,
yellow/white,
yellow

Club-shaped,
absent or rare
"Rat tail",
absent or rare
Variable

Variable Thiamine, inositol +/-
T. violaceum Very slow Glabrous Red,
violet/red,
violet

"Rare"
except pyriform on thiamine agar
"Rare"
Irregular shaped on thiamine agar


Negative Slow positive
after 7 days
Thiamine,
inositol +/-
T. yaoundei Very slow Glabrous Brown,
cream/brown,
diffusible

Absent Absent Negative N/A None

HABITAT

Trichophyton includes anthropophilic, zoophilic and geophilic species. Certain Trichophyton species are cosmopolitan, while others have a limited geographic distribution.

PATHOGENICITY

The genus Trichophyton includes about 22 species of which 11 are commonly associated with tinea of the scalp, the nails, and the skin in humans. It is a common cause of athlete's foot and dermatophytosis. Only 4 species are frequently isolated from animals.

RECOMMENDED MEDIA

Incubate aerobically at 25 degrees C. for 7-21 days.

REFERENCES

1. Hensyl, William R., et al. 1990. Stedman's Medical Dictionary , 25th ed. Williams & Wilkins, Baltimore, MD.

2. St. Germain, Guy and Summerbell, Richard, Ph.D. 1996. Identifying Filamentous Fungi , 1st ed. Star Publishing Company, Belmont, CA.

3. Larone, Davise H. 1995. Medically Important Fungi, A Guide to Identification . 3rd ed. American Society for Microbiology Press, Washington, D.C.

4. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.


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