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Bacterial Meningitis

Español: Meningitis bacteriana

Bacterial meningitis is very serious and can be deadly. Death can occur in as little as a few hours. While most people with meningitis recover, permanent disabilities such as brain damage, hearing loss, and learning disabilities can result from the infection.

There are several types of bacteria that can cause meningitis. Some of the leading causes of bacterial meningitis in the United States include Streptococcus pneumoniae, group B Streptococcus, Neisseria meningitidis, Haemophilus influenzae, and Listeria monocytogenes.

In the United States, about 4,100 cases of bacterial meningitis (caused by S. pneumoniae, group B Streptococcus, N. meningitidis, H. influenzae, and L. monocyteogenes), including 500 deaths, occurred each year between 2003–2007.* [1]

These bacteria can also be associated with another serious illness, sepsis. Sepsis is the body’s overwhelming and life-threatening response to infection that can cause tissue damage, organ failure, and death.


Common causes of bacterial meningitis vary by age group:

Age Group Causes
Newborns Group B Streptococcus, Streptococcus pneumoniae, Escherichia coli, Listeria monocytogenes
Infants and Children Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), Group B Streptococcus
Adolescents and Young Adults Neisseria meningitidis, Streptococcus pneumoniae
Older Adults Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), Group B Streptococcus, Listeria monocytogenes

Risk Factors

Certain people are at increased risk for bacterial meningitis. Some risk factors include:

  • Age
    • Babies are at increased risk for bacterial meningitis compared to people in other age groups. However, people of any age can develop bacterial meningitis. See the table above for which bacteria more commonly affect which age groups.
  • Community setting
    • Infectious diseases tend to spread where large groups of people gather together. Outbreaks of meningococcal disease, caused by N. meningitidis, have been reported from college campuses.
  • Certain medical conditions
    • There are certain medical conditions, medications, and surgical procedures that put people at increased risk for meningitis.
  • Working with meningitis-causing pathogens
    • Microbiologists routinely exposed to meningitis-causing bacteria are at increased risk for meningitis.
  • Travel
    • Travelers to the meningitis belt in sub-Saharan Africa, particularly during the dry season, or to Mecca during the annual Hajj and Umrah pilgrimage may be at increased risk for meningococcal meningitis.
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How it Spreads

The germs that cause bacterial meningitis are spread from person to person. Some bacteria can spread by exchanging of respiratory and throat secretions (saliva or spit) during close (for example, coughing or kissing) or lengthy contact, especially if living in the same household. Fortunately, most of the bacteria that cause meningitis are not as contagious as viruses that cause the common cold or the flu. The bacteria are not spread by casual contact or by simply breathing the air where a person with bacterial meningitis has been. Other meningitis-causing bacteria are not spread person to person, but can cause disease because the person has certain risk factors, such as a weak immune system or head trauma. Unlike other types of bacteria, you can get meningitis from Listeria monocytogenes by eating contaminated food.

Sometimes the bacteria that cause meningitis are spread to other people who had close or lengthy contact with a patient with bacterial meningitis. People who are close contacts of a person with meningococcal or Haemophilus influenzae type b (Hib) meningitis are at increased risk of getting infected and may need preventive antibiotics (see Prevention). Close contacts of a person with meningitis caused by other bacteria, such as Streptococcus pneumoniae, do not need antibiotics. Tell your doctor if you think you have been exposed to someone with meningitis.

Healthy people can carry the bacteria that cause meningitis in their nose or throat with no signs or symptoms of disease; this is called being ‘a carrier’. Sometimes these bacteria can invade the body and cause disease. Most people who ‘carry’ the bacteria never become sick.

Signs and Symptoms


Pregnant women are at increased risk of developing listeriosis an infection caused by the bacteria Listeria monocytogenes. Pregnant women with listeriosis typically experience fever and other symptoms, such as fatigue and aches. Infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn, including meningitis. Pregnant women can reduce their risk of meningitis caused by Listeria monocytogenes by learning what foods to avoid and how to safely prepare and refrigerate food.

Pregnant women who test positive for group B Streptococcus (group B strep) can pass the bacteria to their baby, most often during labor and delivery. A newborn infected with group B strep bacteria can develop meningitis or other life-threatening infections soon after birth. If you are pregnant, you should get screened for group B strep bacteria at 35-37 weeks. Women who test positive for the bacteria will be given antibiotics during labor to prevent infection in a newborn.

Meningitis symptoms include sudden onset of fever, headache, and stiff neck. There are often additional symptoms, such as

  • Nausea
  • Vomiting
  • Photophobia (increased sensitivity to light)
  • Altered mental status (confusion)

The symptoms of bacterial meningitis can appear quickly or over several days. Typically they develop within 3 to 7 days after exposure.

In newborns and babies, the classic meningitis symptoms of fever, headache, and neck stiffness may be absent or difficult to notice. The baby may appear to be slow or inactive, irritable, vomiting or feeding poorly. In young babies, doctors may also look for a bulging fontanelle (soft spot on infant’s head) or abnormal reflexes, which can also be signs of meningitis. If you think your baby or child has any of these symptoms, call the doctor right away.

Later symptoms of bacterial meningitis can be very serious (e.g., seizures, coma). For this reason, anyone who thinks they may have meningitis should see a doctor as soon as possible.


If meningitis is suspected, samples of blood or cerebrospinal fluid (fluid near the spinal cord) are collected and sent to the laboratory for testing. It is important to know the specific cause of meningitis because that helps doctors understand how to treat the disease, and possibly how bad it will get. In the case of bacterial meningitis, antibiotics can help prevent serious illness and reduce the chances a close contact will also develop the disease (depending on which bacteria are causing the infection).

If bacteria are present, they can often be grown (cultured). Growing the bacteria in the laboratory is important for confirming the presence of bacteria, identifying the specific type of bacteria that is causing the infection, and deciding which antibiotic will work best. Other tests can sometimes find and identify the bacteria if the cultures do not.

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Bacterial meningitis can be treated with a number of antibiotics. It is important that treatment be started as soon as possible.


The most effective way to protect you and your child against certain types of bacterial meningitis is to complete the recommended vaccine schedule. There are vaccines for three types of bacteria that can cause meningitis:

  • Neisseria meningitidis
  • Streptococcus pneumoniae
  • Haemophilus influenzae type b (Hib)

Like with any vaccine, the vaccines that protect against these bacteria are not 100% effective. This means that even if you have been vaccinated, there is still a chance you can develop bacterial meningitis.

To help decrease the chance of spreading the bacteria that cause meningitis, antibiotics may be recommended for:

  • Close contacts of a person with meningococcal meningitis
  • Family members of a person who develop a serious Hib infection, especially if there is a person at increased risk living in the house

Your doctor or local health department will tell you if there’s a person at increased risk in your house and whether antibiotics are needed.

Maintaining healthy habits, like not smoking and avoiding cigarette smoke, getting plenty of rest, and not coming into close contact with people who are sick, can also help. This is especially important for young babies, older adults, and people with weak immune systems, since they are at increased risk for serious disease.

Laboratory Methods for the Diagnosis of Meningitis

Laboratory Methods.

This manual summarizes laboratory methods used to isolate, identify, and characterize of N. meningitidis, S. pneumoniae and H. influenzae from the cerebrospinal fluid or blood of patients with clinical meningitis or bacteremia.

View list of chapters


  1. Thigpen MC, Whitney CG, Messonnier NE, Zell ER, Lynfield R, Hadler JL, et al. Emerging Infections Programs Network. Bacterial meningitis in the United States, 1998-2007. N Engl J Med. 2011;364:2016-25.


*This is the most recent data to date.

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