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School of Molecular & Biomedical Science |
Trichophyton mentagrophytes var. quinckeanumOn Sabouraud's dextrose agar, colonies are flat or slightly raised and folded, white to cream, suede-like in texture with a pale yellow-brown to pinkish brown reverse. A characteristic pungent "mousy" odour may be present. Numerous microconidia, predominantly slender clavate when young, are borne laterally along the sides of hyphae. With age the microconidia become broader and pyriform, and some subspherical forms are present. Occasional to moderate numbers of smooth-walled, multiseptate, clavate macroconidia may be present. RG-2 organism.
Kaminski's Dermatophyte Identification Scheme:Littman Oxgall Agar (Difco): Raised, dome-like bluish-grey, suede-like colony with a narrow flat, greyish-white, suede-lik Lactritmel Agar (Mycopathologia 91:57-59, 1985): Flat, white to cream, suede-like to powdery colony with either no reverse pigment or a pale yellow-brown to pinkish-brown reverse. Numerous slender clavate to pyriform (depending on age of sub-culture) microconidia and occasional to moderate numbers of smooth, thin-walled, clavate macroconidia are present. Sabouraud's Dextrose Agar with 5% NaCl: Heaped up and much folded white suede-like colony with very pale yellow-brown reverse. No submerged fringe. 1% Peptone Agar: Raised white suede-like to downy colony with no reverse pigment. Hydrolysis of Urea: Positive within 7 says (usually very rapid 2-3 days). Vitamin Free agar (Difco Trichophyton Agar No.1): Flat, white to cream, suede-like colony with either no reverse pigment or a pale yellow-brown reverse. i.e. No special nutritional requirements. Hair Perforation Test ("in vitro"): Positive in 7 to 10 days. T. mentagrophytes var. quinckeanum may be distinguished from T. mentagrophytes by (a) its characteristic culture appearance on Littman Oxgall agar (i.e. raised, dome-like, bluish-grey suede-like colony with a narrow flat, greyish-white, suede-like border and no diffusible or reverse pigment); and on Sabouraud's salt agar (typically heaped and folded white Suede-like colony, but with no distinctive dark reddish-brown submerged fringe and reverse pigment as seen on T. mentagrophytes); (b) microscopic morphology showing numerous slender clavate with some pyriform microconidia and moderate numbers of smooth thin-walled, clavate macroconidia; (c) a rapid urease test, usually 2 to 3 days; and (d) cultures often have a characteristic pungent "mousy" odour. Clinical significance:Trichophyton mentagrophytes var. quinckeanum is a zoophilic form of T. mentagrophytes. It causes a "mouse favus" on mice, and this is seen as thick, yellow, saucer-shaped crusted lesions up to 1 cm in diameter called scutula. Invaded hairs are rarely seen but they may show either ectothrix or endothrix infection. Infected human hairs do not fluoresce under Wood's ultra-violet light, but very occasional hairs from experimental lesions in guinea pigs may show a pale yellow fluorescence. The geographical distribution of this dermatophyte is difficult to establish, but its probably world-wide. It is often associated with mice plagues in the Australian Wheat Belt. Mycosis: DermatophytosisFurther 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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