Diagnosis of Fungal Skin Infection Laboratory Management ( ada gambar
&1)
Fungi are usually larger than bacteria and in skin specimens they can be
seen by direct icroscopy provided the material is first softened and
cleared with a strong alkali to digest the keratinn surrounding the fungi so
that the hyphae and spores can be seen.
Common skin fungal pathogens include;
T.schoenleinii
Microsporum audouinii
Tricophyton verrucosum, T. rubrum, T.pedis, T.cruris, C. albicans
Fungal sample collection and processing
In skin infections a fungal lesion usually spreads outwards in concentric fashion with healing in the central region. Material should therefore be collected by scraping out wards from the edges of the lesions with a scalpel blade; when there is minimal scaling as, for example, with lesions of the glabrous skin, it is preferable and sometimes necessary to use celotape to remove adequate material for examination.
Specimens from the scalp are best obtained by scraping with a blunt scalpel so that the sample includes hair stubs, contents of plugged follicles and scales. Hairs, which have been cut, rather than plucked, are seldom satisfactory. Nail clipping or scraping could be used for nail infections.
In all cases, cleaning the site with 70% alcohol before taking the specimen may be helpful and should be done if greasy ointments or if powders have been use for treatment. Material is best collected in to folded squares of paper. This permits drying of the specimen,reduces bacterial contamination and also provides conditions under which specimens may be stored for long periods with out appreciable loss in viability of fungi and parasites.
Baca Juga : Superficial Fungal Infection
Direct Microscopy
Use dimethyl sulphoxide – KOH reagent (DMSO – KOH) The addition of DMSO to KOH enables specimens to be examined immediately or after only a few minutes
Procedure
1. Place a drop of 20% potassium hydroxide solution on a slide
2. Transfer the specimen (Skin scrapings) to the drop of KOH, and cover with a cover glass. Place the slide in a Petri dish, or other container with a lid, together with a damp piece of filter paper or cotton wool to prevent the preparation from drying out
Note: To assist, clearing skin scales should not be more than 2mm across
-Skin scales and crusts usually take 20-30 minutes when using KOH without DMSO.
-Clearing keratin can be hastened by gently heating the preparation over the flame of a sprit lamp or pilot flame of a Bunsen burner, taking care to prevent drying or splatter of the corrosive KOH solution. Heating reduces the clearing time using KOH-DMSO reagent.
3. As soon as the specimen has cleared, examine it microscopically using 10x and 40 x objectives with the condenser iris diaphragm closed sufficiently to give good contrast.
Note: If too intense a light source is used the contrast will not be adequate and the unstained fungi will not be seen.
Dermatophytes in skin scales : look for branching septate hyphae with angular or spherical arthrospores, usually in chains. All species of ringworm fungi have a similar appearance
Fungi need to be distinguished from epidermal cell outlines, elastic fibers, and artifacts such as intracellular cholesterol (mosaic fungus) and strands of cotton or vegetable fibers. Ringworm fungal hyphae can be differentiated from these structures by their branching, uniform width, and cross- walls (septa), which can be seen when using 40-xobjective. In Superficial Candidiasis, the fungus may be seen as budding yeast cells and in the majority of instances mycelium is also present. (Figure: 3)
Thanks For Visiting ! Keep Your Healthy !
0 comments:
Post a Comment