Meningitis is an acute inflammation of the protective membranes covering the brain and spinal cord. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms. However, acute bacterial meningitis is the most common form of meningitis and covers approximately 80 percent of all cases. The infection is caused by both Gram negative and Gram positive bacteria which include Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenza and Listeria monocytogenes.
The infection can cause the tissues around the brain to swell. This in turn interferes with blood flow and can result in paralysis or even strokelike symptoms. The classic diagnostic signs consist of nuchal rigidity, sudden high fever, and altered mental status. Despite the availability of potent new antibiotics, the mortality rate caused by acute bacterial meningitis remains high. In USA the mortality ranges from 15-20% but in the developing countries the mortality ranges from 40-50%.