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

5. Bacteriology 2153. Load an improved Neubauer counting chamber (see Fig. 9.40), allow the spermto settle and then count in the four corner squares, as for a leukocyte count (seesection 9.6.3). The formula for calculation is similar to that used for leukocytes,except that the sperm count is per ml instead of per mm 3 , so an additional multiplicationfactor of 1000 is needed.Number of sperm ml =n ¥ 10 ¥ 20 ¥ 10004where n = number of sperm counted.The normal sperm count is between 60 million and 150 million per ml (100–500 million/ml according to some sources). Patients with sperm counts below60 million per ml definitely have low counts, though they may still be fertile.5.8 Examination of vaginal dischargeVaginal discharge is examined by microscopy to exclude infections with gonococci,Candida albicans and Trichomonas vaginalis, which cause bacterial vaginosis, vulvovaginalcandidiasis and trichomoniasis, respectively.5.8.1 Materials and reagents●●●MicroscopeMicroscope slidesCoverslips● Sodium chloride, 0.85% solution (reagent no. 53).5.8.2 MethodCollection of specimensThe specimen should be collected by a physician or specialist nurse.Preparation of slides1. Make a smear of the discharge on a slide and allow it to air-dry. Stain the smearwith Gram stain (see section 5.3.1) and examine for Candida albicans.2. Transfer a small sample of discharge to a second slide, add a drop of salinesolution and cover with a coverslip. Look for gonococci and Trichomonas vaginalistrophozoites in this preparation.5.8.3 Microscopic examinationExamine the Gram-stained slide using the ¥ 40 objective and the ¥ 100 oilimmersionobjective. Candida albicans appears as large Gram-positive yeasts, oftenwith budding or short lengths of mycelium (see Fig. 5.13).Examine the saline preparation as soon as possible using the ¥ 10 and the ¥ 40objectives. Use a microscope with the iris diaphragm closed to give good contrast.Do not allow the specimen to dry out. Gonococci are Gram-negative and appear assmall dots (see Fig. 5.12). Trichomonas vaginalis trophozoites appear as highlymotile flagellates measuring 8–20mm, with an undulating membrane and a prominentnucleus.