Page 122 - LECTURE NOTES

7. Cover the smear with neutral red (safranin) stain for 2 minutes

8. Wash off the stain with clean water
9. Wipe the backs of slide clean, and place it in a draining rack for the smear to

air-dry.
10. Examine the smear microscopically, first with the 40-x objective to check the

staining and to see the distribution of material and then with the oil immersion
objective to report the bacteria and cells.

Results:

- Gram positive bacteria ……………………………… Dark purple
- Yeast cell ………………………………………………Dark purple

- Gram negative bacteria …………………………….. Pale to dark red
- Nuclei of pus cells …………………………………… Red

- Epithelial cells ……………………………………….. Pale red

Reporting gram smears

The report should include the following information;

- Numbers of bacteria present, whether many, moderate, few or scanty,
- Gram reaction of bacteria, whether gram positive or gram negative

- Morphology of bacteria, whether cocci, diplococci, streptococci, rods, or
coccobacilli. Also, whether the organisms are intracellular or extra cellular.

- Presence and number of pus cells

- Presence of yeast cells and epithelial cells

5.4.3. Laboratory features of M.leprae

Morphology

M. laprae is a non-motile, non-sporing, straight or slightly curved rod measuring 0.2-0.5
x 5-8μm bacteria. Pointed or enlarged ends are sometimes seen. The organisms can be

found singly, in clusters, and in large groups within macrophage cells.

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