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School of Molecular & Biomedical Science |
Microsporum cookeiTeleomorph: Arthroderma cajetani Colonies are flat, spreading, buff to pale brown, powdery to suede-like, with slightly raised and folded centre and some radial grooves. Reverse pigment dark reddish brown. Numerous large, very thick-walled, echinulate (rough) elliptical macroconidia with predominantly 5-6 septa but may be from 2-8 septa. Occasional spirals may be seen. Moderate numbers of mainly slender clavate with some pyriform macroconidia are present. The macroconidia are quite characteristic and diagnostic of M. cookei and further tests are not necessary. The thick walls and usually larger size of the macroconidia distinguished M. cookei from M. gypseum. RG-1 organism.
Lactritmel Agar: Flat, buff-coloured, suede-like to powdery colony with a deep red-brown reverse. Microscopic morphology as described above for the primary culture. Vitamin Free Agar (Trichophyton Agar No.1): Good growth indicating no special nutritional requirements, pinkish-buff-coloured, suede-like colony with a deep magenta red reverse. Hair Perforation Test: Positive. Key Features: distinctive macroconidial morphology and culture characteristics. Clinical significance:Microsporum cookei is a geophilic fungus which has been isolated from hair of small mammals showing no clinical lesions. Infection has been reported in rodents, dogs and rarely in humans. It is not known to invade hair in vivo, but produces hair perforations in vitro. M. cookei has a world-wide distribution. 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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