DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 205
Trichophyton quinckeanum (Zopf) MacLeod & Münde
Synonymy: T. mentagrophytes var. quinckeanum (Zopf) J.M.B. Smith & Austwick.
Trichophyton quinckeanum causes “mouse favus” on mice, 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 have shown a pale yellow fluorescence. The
geographical distribution of this dermatophyte is difficult to establish, but is probably
worldwide. It is often associated with mice plagues in the Australian Wheat Belt.
RG-2 organism.
Morphological Description: Colonies are generally flat, white to cream in colour, with
a powdery to granular surface. Some cultures show central folding or develop raised
central tufts or pleomorphic suede-like to downy areas. Reverse pigmentation is usually
a yellow-brown to reddish-brown colour. Numerous microconidia are borne laterally
along the sides of hyphae, and are predominantly slender clavate when young. With
age the microconidia become broader and pyriform to spherical in shape. Occasional
to moderate numbers of smooth, thin-walled, multiseptate, clavate to cigar-shaped
macroconidia may be present. Varying numbers of spherical chlamydospores and
spiral hyphae may also be present.
Confirmatory Tests:
Littman Oxgall Agar: Raised, dome-like bluish-grey, suede-like colony with a narrow
flat, greyish-white, suede-like border. No diffusible or reverse pigment is present.
Lactritmel Agar: 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 subculture) microconidia and occasional to
moderate numbers of smooth, thin-walled, clavate macroconidia are present.
Sabouraud’s Dextrose Agar with 5% salt: Heaped 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 days (usually very rapid 2-3 days).
Vitamin Free Agar (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: Positive in 7 to 10 days.
Key Features: Culture characteristics, microscopic morphology, and rapid urease test.