Culturing for dermatophytes

Fungal culture using skin scales and plucked hairs is necessary when dermatophytosis is suspected. Hairs should be plucked from the lesions using forceps and placed in envelopes or sterile universal containers for transport to the laboratory. It is also useful to submit scales and crusts removed by scraping with a scalpel blade.

An alternative method is to use various forms of brushes for sampling wide areas of the hair coat. This is a modification of the technique described by MacKenzie who investigated the spread of ringworm in a girl's school by culturing their hairbrushes! Toothbrushes, sterilised carpet squares or plastic Denman brushes can be brushed through the haircoat and the bristles stabbed into the culture medium.

Scales and hairs are inoculated onto Sabouraud's dextrose agar, usually containing other inhibitors of microbial growth such as chloramphenicol (to inhibit cutaneous bacteria) and cycloheximide (to inhibit saprophytic fungi). Plates are incubated at 26°C for 2-4 weeks.