Mycology

Mycology can be used to identify superficial fungal infections including yeasts (candidiasis and pityriasis versicolor), dermatophytes (ringworm/tinea – tinea unguium) or moulds (e.g. Scopulariopsis) using scales scraped from the edge of a scaly lesion, nails using a blunt instrument such as blunt scalpel blade or blunt edge of a stitch cutter. Scrapings of scale should be taken from the leading edge of the rash (as this is where active spores are most likely to be found) after the skin has been cleaned with alcohol, such as surgical spirit or 70% alcohol. This minimises contamination and is an aid to microscopy if greasy ointments or powders have been applied. Samples can be collected on kits providing black paper envelopes (e.g. Dermapak), which can be easily transferred to the lab. It is essential to have an adequate sample and provide full clinical details if the test is to be successful; whilst the precise quantity is difficult to quantify, as a general rule it is worth including as much material as possible so that full laboratory investigations can be carried out. It is always useful to have enough skin or nail to repeat the culture if necessary. Sample the discoloured, dystrophic or brittle parts of the nail only, gently digging as far back as possible from the distal part of the nail. For dermatophyte infections, samples should be taken from the distal nail and from debris under the nail (subungual debris). For superficial onychomycosis, the scraping should be from the nail surface and for Candida infections (e.g. a chronic paronychia) a swab should be taken from the proximal nail fold.

Hair can be plucked from the affected area with forceps; the infected hairs come out easily. The scalp may then be scraped with a blunt scalpel. Preferably, the sample should include hair stubs, the contents of plugged follicles and skin scales. Hair cut with a scissors is unsatisfactory as the focus of infection is usually below or near the surface of the scalp.