Fungal microscopy and culture - skin, hair, nails

Last updated: Saturday, 03, April, 2004

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Item Process
Specimen

Skin scrapings, hair (plucked), nail clippings. As much material as feasible should be provided.

The growing edge of the infection is the best area to sample.

Skin biopsy: fresh and formalin fixed.

Method

Microscopy: keratinised tissues are treated with potassium hydroxide and stained with eg, lactophenol blue or fluorescent dyes to detect hyphae of dermatophytes.

Paraffin sections of biopsies are occasionally required.

Culture: many pathogenic fungi will grow slowly on conventional media but may be recovered more reliably on special fungal media, which require incubation for up to 4 weeks.

Susceptibility tests to antifungal agents are unreliable but can occasionally be of value to detect resistance.

Application

Investigation of suspected yeast infection, tinea, ringworm (dermatophyte infection).

Suspected deep fungal skin infections (biopsy required) eg, sporotrichosis, mucormycosis, chromomycosis, mycetoma.

Interpretation

Typical microscopic appearance indicates fungal infection but does not identify the particular fungal species. Culture of yeast or fungus provides species identification.

Malassezia furfur, the causative agent of pityriasis versicolor, is an exception. It has a characteristic appearance on microscopy and does not grow without special supplements, and is therefore identified on microscopy alone.

Reference

Summerbell RC. In: Murray PR et al eds. Manual of Clinical Microbiology. 8th ed. ASM Press 2003.