Manual of basic techniques for a health laboratory - libdoc.who.int

6. Mycology 16.1 Examination of skin and hair for fungiRingworm or tinea is a fungal infection of the skin. It can be found on the surfaceof the body, the scalp and the nails and between the toes. Cross-infection betweenhumans frequently occurs and infection can also be acquired from infected animalsor soil.The circular lesions on the skin consist of a mass of branching hyphae; infected hairand nails may also contain spores of fungi.6.1.1 Materials and reagents●●●●●●●●●●MicroscopeMicroscope slides (or dark paper)CoverslipsScalpelTweezersPetri dishBunsen burner or spirit lampCotton wool swabCotton wool70% Ethanol● Lactophenol cotton blue mounting solution (reagent no. 33)● Potassium hydroxide, 20% solution (reagent no. 45).6.1.2 Method 2Collection of specimens1. Clean the infected area with a cotton wool swab soaked in ethanol.2. Use a sterile scalpel to gently scrape the edge of a lesion and collect some skinscales on to a glass slide or on to a piece of dark paper on which the scales can bemore easily seen. Also collect a few broken or damaged hairs from the infectedareas of the scalp using broad tweezers and place them on the slide.3. Place a drop of lactophenol cotton blue mounting solution and a drop of 20%potassium hydroxide on to the scales and hair (Fig. 6.1). Cover with a coverslip.The strong alkali will dissolve the keratin in the tissue, enabling hyphae andspores to be seen.Note: Potassium hydroxide is a corrosive fluid and should not be allowed totouch the skin.1A description of the method used for the identification of Candida albicans in vaginal dischargeis provided in section 5.8.2Tinea infection can also be identified by examining the patient in a dark room illuminated withultraviolet light. The hairs infected with tinea will appear fluorescent.225