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

8. Examination of cerebrospinal fluid (CSF) 261●●●Surrounded by a capsule, which is not visible with Gram stainNot intracellularUsually many in number.Haemophilus influenzae (especially in young children) (Fig. 8.14)● Gram-negative●●Small bacilli (coccobacilli)Not intracellular● Often numerous.In all the above-mentioned forms of meningitis the leukocytes present areneutrophils.Fig. 8.14 HaemophilusinfluenzaeGram-positive bacilliVery rarely found. May belong to the Listeria group. Culture is essential.Ziehl–Neelsen-stained smear for tuberculous meningitisMethodIf tuberculous meningitis is suspected, the CSF should be left to stand. If a clotforms, it should be removed, spread on a slide and stained with Ziehl–Neelsenstain, as described in section 5.3.3.If organisms are seen (Fig. 8.15), report the smear as “acid-fast bacilli present”.Fig. 8.15 Acid-fast bacilliFungi in the CSFVery rarely, fungi (Cryptococcus neoformans and Candida albicans) may be observedin a smear stained with Gram stain.Cryptococcus neoformans may be found in cloudy CSF with lymphocytes.MethodMix on a microscope slide:— one drop of CSF deposit— one drop of Indian ink.Examine the mixture between a slide and a coverslip.Cryptococcus neoformans appears as follows (Fig. 8.16):— round budding spores containing greyish granulations;— each group of 1–3 spores is surrounded by a colourless capsule.Candida albicans may be found in an unstained wet preparation of CSF deposit. Itappears as follows (Fig. 8.17):— oval budding spores— short mycelium filaments.Fig. 8.16 CryptococcusneoformansFig. 8.17 Candida albicans8.3.4 Determination of glucose concentrationGlucose concentrations in the CSF are normally about 60% of those in blood, i.e.2.5–4.2mmol/l (45–75mg/100ml).In patients with meningitis (especially purulent and tuberculous meningitis), theconcentration of glucose in the CSF is greatly reduced.