Page 126 - LECTURE NOTES

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.

5.5.2. 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

ƒ Skin scales and crusts usually take 20-30 minutes when using KOH
without DMSO.

ƒ 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.

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