The infection then settles in the fluid and the membranes around the brain. The resulting inflammation is responsible for many of the symptoms of meningitis. It may also play a role in some of the complications. Bacterial meningitis is caused by a bacteria that usually enters the body through the person's nose or throat. The bacteria can be transmitted to newborns during labor and delivery.
Many people can have the bacteria in their noses or throats without developing meningitis.
The bacteria are more likely to cause meningitis in very young infants. People with a weakened immune system, such as those with AIDS, are also at high risk. It is one of the recommended immunizations given to children. Due to this vaccine, this once-common cause of meningitis is now almost nonexistent. Vaccines do exist for other meningitis-causing organisms such as Neisseria meningitidis and Streptococcus pneumoniae.