Bacterial meningitis can be caused by about 50 different kinds of bacteria. The most common culprits include:
- Group B Streptococcus (group B strep). This bacterium most commonly affects infants less than 2 months old
- Streptococcus pneumoniae (S. pneumoniae). This bacterium most commonly affects infants, young children, and adults in the United States
- Neisseria meningitidis (N. meningitidis). This bacterium most commonly affects teenagers and young adults
Other types of bacteria that less commonly cause bacterial meningitis include:
- Haemophilus influenzae (H. influenzae). This bacterium was once the leading cause of bacterial meningitis in children, but it’s rare now due to routine vaccines
- Listeria monocytogenes (found in unpasteurized cheeses, hot dogs and lunchmeats)
- Escherichia coli (E. coli)
Some types of bacteria that cause meningitis can be passed to other people through saliva or mucus, via coughing, sneezing, kissing, or other forms of close contact.
It’s not uncommon for people to carry bacteria that causes bacterial meningitis in their nose and throat, and while you may not get sick, you can still spread the bacteria to other people who could get an infection.
Risk Factors
Risk factors for bacterial meningitis include:
- Age, especially children between the ages of 1 month and 2 years
- Substance use disorder
- Chronic nose or ear infections
- Head injury
- Pneumococcal pneumonia
- Living in crowded quarters, such as in college or boarding school dormitories, or military barracks
- Diseases, medication, or surgical procedures that weaken the immune system
- Having had your spleen removed
- Having had brain or spinal surgery or a widespread blood infection
