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Classify dermatophytes

 

                                           Classify Dermatophytes


It is a group of filament us fungi that infect superficially I,e skin , hair and Nail. The clinical condition known as dermatophytes popularly called Toenia and ring worm.

                   It is classified in 3 genera:-

1. Trichophyton 2. Mycosporum 3. Epidermophyton based on Macroconidia.

Ø  In lesion dermatophytes appear as Hyphae and Artherospore. In culture on SDA medium shows characteristic colonies consisting of septate hyphae and two types of asexual spare, Microconidia ansd Macroconidio.

1. Trichophyton:- Colonies may be powdery, velvety or waxy. Microconidia are ab undant and are arranged in cluster along the hyphae and macroconidia are relatively scanty. They are generally elongated with blunt end. Some species shows spiral hyphae and racket mycelium.

2. Mycosporum:- Colonies are velvety or powdery with white to brown pigmentation. Microconidia are relative scanty. Macroconidia are large multicellular and spindle shaped structure, infect hair and skin.

3. Epidermophyton:- Colonies are powdery and greenish yellow in colour. Microconidia are absent. Microconidia are multinucleated. Pear shaped are typically arranged in cluster attached to the skin and nail.

       Pathogenicity:- Dermatophytes grow only on the Keratinized tissue of the layer of skin. They do not penetrate into the living tissue. The fingal product give rise to local inflammation or a HSR.

          Lab diagnosis:- The routine method of diagnosis is by the examination of lesions in KOH mounts.

        i) Scrapping are taken from the edge of ring worm and mount in KOH. Heated and shows branched septate hyphae microscopically.

       ii) Examination of infected hair in UV light, Ectothrix and Endothrix with arthrospore.

      iii) Demonstration of fugus in nail mount in KOH for 1 day for clearing.

      iv) Special Identification by inoculation on SOA and colonies shows may appear in only 1-3 weeks.

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