MCS fungal

Keywords: Fungal microscopy culture sensitivities, Fungal microscopy, Fungal culture, Mycology culture, Skin scrapings

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 cotton 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. 2003. ASM Press.