Dermatophytes

Mycology

Dermatophytes Three main genera

1-Genus Microsporum

infect skin & hair Example :M. canis(from animal) M.gypsium(from soil) M.audouinii(from human)

Culture of Microsporum

Colonies :developed rapidly (cottony or wooly or powdery mycelium). Color :white to shades of brown Reverse side :yellow to orange brown

Microscopy of Microsporum

Macroconidia are large ,thick-walled, rough ,spindle shape & multicellular(6to 15 celled in M.Canis) . Less numerous microconidia.

Microsporum spp.

Genus Trichophyton


Culture of T.verrocosum

Trichophyton spp.

Genus Epidermophyton
Only one sp. E.Floccosum This fungus attack skin & nails (but not hair).

Culture

Colonies are velvety with central radiating furrows. Color is yellow to green Reverse side is yellow to tan.

Microscopy

Macroconidia are large ,multiseptate (2 to 6 celled), smooth rounded wall racquet hyphae are common & no microconidia are formed.

Mycology

Type of hair invasion

Unicellular fungi /Candida

Yeast on culture

Microscopical appearance

1-A lactophenol slide mount shows oval, budding cells & some times some pseudohyphae when taken from old culture. 2-Gram stain shows Gram positive yeast cells (large cells & may arranged in clusters).

Identification

1-Chlamydospore formation: Corn meal agar plus Tween 80 are used for production of chlamydospores (thick wall asexual spore). After inoculation ,do incubation for 3 days & then examine. 2-Germ tube method (serum tube method): is produced after inoculation of low concen.

Budding yeast / germ tube Budd Budding Yeast/Germ

Cryptococcus
C.neoformansis the pathogenic sp. It is a yeast fungi & can be differentiated from candida by 2 main featurea 1-Capsulated 2-Urease positive