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

108 Manual of basic techniques for a health laboratoryMaterials and reagents (Fig. 4.2)●●●●●MicroscopeMicroscope slidesCoverslipsWooden applicators or wire loops (0.45mm, nickel–chromium alloy wire)Grease pencils● Sodium chloride, 0.85% solution (reagent no. 53)● Lugol iodine, 0.5% solution (reagent no. 37)●Acetic acid, 50% solution (reagent no. 3), diluted 1:1 with distilled water● Methylene blue solution (reagent no. 39)● Eosin, 2% solution in saline (reagent no. 24).Method1. Prepare a 1:1 mixture of Lugol iodine solution and acetic acid solution (dilutedas above). Dilute the mixture with four volumes of distilled water and stir.2. Take a dry microscope slide and label it with the name or number of thepatient.3. Put:— one drop of sodium chloride solution warmed to 37°C in the middle ofthe left half of the slide; and— one drop of the iodine–acetic acid solution in the middle of the right halfof the slide (Fig. 4.3).4. Using an applicator or wire loop, take a small portion (about 2–3mmdiameter) of the stool.(a) If the stools are formed, take the portion from the centre of the sample(Fig. 4.4) and from the surface to look for parasite eggs.(b) If the stools contain mucus or are liquid, take the portion from the mucuson the surface or from the surface of the liquid to look for amoebae.5. Mix the sample with the drop of sodium chloride solution on the slide.6. Using the applicator or wire loop, take a second portion of stool from the specimenas described above and mix it with the drop of iodine–acetic acid solution.Discard the applicator (or flame the wire loop) after use.7. Place a coverslip over each drop (apply the coverslips as shown in Fig. 4.5 toavoid the formation of air bubbles).8. Examine the preparations under the microscope. For the saline preparationuse the ¥ 10 and ¥ 40 objectives and a ¥ 5 eyepiece. As the eggs and cysts areFig. 4.2 Materials and reagents for directmicroscopic examination of faeces forparasitesFig. 4.3 Adding a drop of saline and adrop of iodine suspension to theslide