Bacterial meningitis: vaccines and prophylaxis

Viral, bacterial and fungal infections are the most common causes of meningitis. However, subarachnoid haemorrhage, chemicals, cancers and certain noninfectious inflammatory conditions may also lead to meningitis. In this article we discuss bacterial meningitis, with specific emphasis on the most common causes of bacterial meningitis occurring after the neonatal period, namely Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae. The brain and spinal cord are covered by membranes called the meninges. The meninges are made up of three separate membranes namely the dura mater, the arachnoid and the pia mater. The dura mater is situated directly beneath and adherent to the skull. The pia mater is the membrane that covers the brain and the arachnoid is located between the dura mater and the pia mater. The region between the arachnoid and the pia mater is where the cerebrospinal fluid (CSF) passes and is called the subarachnoid space. Meningitis is an inflammatory disease of the pia mater and the arachnoid membranes including the CSF in the subarachnoid space and in the cerebral ventricles.