The examination of cerebrospinal fluid (CSF) is an essential step in the diagnosis of bacterial and fungal meningitis and CSF must always be considered as a priority specimen that requires prompt attention by the laboratory staff.
Normal CSF is sterile and clear, and usually contains three leukocytes or fewer per mm3 and no red blood cells. The chemical and cytological composition of CSF is modified by meningeal or cerebral inflammation, i.e., meningitis or encephalitis. Only the microbiological examination of CSF will be discussed here, although the CSF leukocyte count is also of paramount importance.
The most important causal agents of meningitis are listed in Table 5 according to age of the patient, but it should be kept in mind that some overlap exists.