Definition of Meningitis, bacterial

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Meningitis, bacterial: Inflammation of the meninges due to a bacterial infection. Haemophilus influenzae type b (Hib) was the leading cause of bacterial meningitis before the 1990s, but new vaccines given to children as part of their routine immunizations have reduced the occurrence of invasive disease due to H. influenzae. Streptococcus pneumoniae and Neisseria meningitidis are now the leading causes of bacterial meningitis.

High fever, headache, and stiff neck are common symptoms of meningitis in anyone over the age of 2 years. Other symptoms may include nausea, vomiting, discomfort looking into bright lights, confusion, and sleepiness. In newborns and small infants, the classic symptoms of fever, headache, and neck stiffness may be absent or difficult to detect, and the infant may only appear slow or inactive, or be irritable, have vomiting, or be feeding poorly. As the disease progresses, patients of any age may have seizures.

The diagnosis is confirmed by examining a sample of spinal fluid obtained by a lumbar puncture (spinal tap). Treatment is started as early as possible. Appropriate antibiotic treatment of most common types of bacterial meningitis should reduce the risk of dying from meningitis to below 15%, although the risk is higher among the elderly.

Some types of bacterial meningitis are contagious. The bacteria are spread through respiratory and throat secretions. This is true with meningitis caused by Neisseria meningitidis (also called meningococcal meningitis) or Hib. People in the same household or day-care center, or anyone with direct contact with a patient's oral secretions (such as a boyfriend or girlfriend) are at increased risk of acquiring the infection and should receive antibiotics to prevent them from getting the disease. Antibiotics for contacts of a person with Hib meningitis disease are no longer recommended if all contacts 4 years of age or younger are fully vaccinated against Hib disease.

There are vaccines against Hib and against some strains of N. meningitidis and many types of Streptococcus pneumoniae. The vaccines against Hib are considered safe and highly effective. There is also a vaccine that protects against four strains of N. meningitidis, but it is not routinely used in the US and is not effective in children under 18 months of age. The vaccine against N. meningitidis is sometimes used to control outbreaks of some types of meningococcal meningitis in the US. A vaccine to prevent meningitis due to S. pneumoniae (also called pneumococcal meningitis) can also prevent other forms of infection due to S. pneumoniae. The pneumococcal vaccine is not effective in children under 2 years of age but is recommended for all persons over 65 years of age and younger persons with certain chronic medical problems.