Page 125 - LECTURE NOTES

5. Wash off the stain with clean water; wipe the back of the dry slide (do not blot-

dry). Protect it from direct sun light.
6. Examine the smear microscopically, first with the 40x objective to see the

distribution of material and then with the oil immersion to look for acid-fast bacilli.

Result
M. leprae …………………………….. Red solid bacilli or beaded forms,

occurring singly or in masses

Macrophage cells ……………………… green*
*Blue if methylene blue counter stain has been used

- Reporting M.leprae smear;

Report the smear as ‘positive’ if M.Leprae bacteria are seen or ‘Negative’

if no bacteria are seen after examining entire smear or at least 100 high power
microscope fields.

5.5. Diagnosis of Fungal skin infection

Fungi are usually larger than bacteria and in skin specimens they can be seen by direct
microscopy provided the material is first softened and cleared with a strong alkali to

digest the keratin 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

5.5.1. 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.

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