Page 118 - LECTURE NOTES

5.2. Learning Objectives

After completion of this module the lab personnel will be able to:

ƒ Describe how to collect, handle & label specimens from the skin
ƒ Describe routine concepts of laboratory diagnosis of skin diseases

ƒ Describe and demonstrate the laboratory procedures for M.leprae identification
using Ziehl-Neelsen technique

ƒ Describe & demonstrate how to prepare gram stain for identification of bacterial

gram reaction.
ƒ Mention the main essential laboratory diagnostic methods for diagnosis of cutaneous

leishmaniasis and skin fungal infections
ƒ Describe the microscopic appearance of the diagnostic stages of Leishmania and

fungal structures
ƒ Mention the techniques which are used for the diagnosis of virus in skin disease

5.3. Skin Infection

Viruses, bacteria, fungi, or parasites can cause skin disease. The most common
bacterial skin pathogens are staphylococcus aureus and group A-ß hemolytic

streptococci. Herpes simplex is the most common viral skin disease. Of the
dermatophytic fungi, Trichophyton rubrum is the most prevalent cause of skin infections.

Clinical examination and staining and/or culturing of a specimen of pus or exudates are
often adequate for bacterial diagnosis.

Microscopic examination of a KOH preparation of skin scales, nail scrapings, or loose

hair is useful for fungal infection. Ultraviolet light (Wood’s lamp) is helpful in the

diagnosis of erythrasma, and some fungal infections. Other advanced diagnostic tools
include culture and serological testes. For parasite skin infections a skin slit smear

stained with Giemsa stain is used for the diagnosis of Cutaneous Leishmaniasis.

For viral infections, stained smears of vesicle fluid are examined under the microscope

or typical cytopathology.

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