What Is Bacterial Meningitis?

A serious illness that affects the membranes around the brain and spinal cord

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Meningitis refers to inflammation of the meninges, the thin membranes that surround the brain and spinal cord. When the meninges become swollen, they can press on the brain and spinal cord, causing serious complications. Bacterial meningitis, also known as pyogenic meningitis, is a type of meningitis caused by a bacterial infection.

Early symptoms of bacterial meningitis may resemble those of a cold, such as a headache and fever, but they may change quickly. Bacterial meningitis can be life-threatening and requires treatment with antibiotics right away. It can cause permanent disabilities, and is considered a medical emergency.

Those with a weakened immune system are at higher risk of developing bacterial meningitis. Vaccines are the most effective way to protect yourself against bacterial meningitis.

Young woman patient lying on bed while closing her eyes in hospital

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Symptoms

The symptoms of bacterial meningitis often start out mild, and may resemble the symptoms of a cold or upper respiratory infection. They usually appear about three to seven days after exposure to bacteria.

Symptoms can quickly progress to a high fever and severe headache with a very stiff neck. If you are unable to look down to touch your chin to your chest, see your doctor right away. 

Many people also experience nausea and vomiting. Other common symptoms include photophobia and confusion. Later symptoms of meningitis are life-threatening, and include seizures and coma. 

Bacterial Meningitis in Babies and Children

In newborns, look at the fontanel on their head. This soft spot may appear to be bulging. If you notice a bulging fontanel or abnormal reflexes in your newborn, seek emergency treatment. Infants may appear to react slower than usual and seem irritable. They may not be interested in feeding and could vomit after nursing or drinking milk or formula from a bottle. 

Causes

Bacterial meningitis is caused by a bacterial infection. The bacteria can be spread to people through food or close contact. The most common types of bacteria that can lead to bacterial meningitis in the United States include:

  • Streptococcus pneumoniae
  • Group B Streptococcus
  • Neisseria meningitidis
  • Haemophilus influenzae (Hib)
  • Listeria monocytogenes

Although these infections can cause meningitis, they usually don't. So just being infected with one of these organisms doesn't mean you are at high risk of meningitis.

Hib and S. pneumoniae are spread when a sick person coughs or sneezes in close contact with others.

N. meningitidis is spread through respiratory or throat secretions like saliva. It is usually shared through kissing, coughing, or living in close contact. 

Group B Streptococcus can be passed from mother to infant during childbirth. All pregnant women should be tested for this bacteria prior to giving birth. If they are positive, antibiotics are given to prevent the newborn from becoming infected.

E. coli can be spread through contaminated food when the person preparing it does not wash their hands after using the bathroom. It can also be spread from mother to infant during childbirth. 

L. monocytogenes is also spread through contaminated food, and is dangerous to the fetus if a pregnant mother is exposed. 

Groups Most At Risk Type of Bacterial Infection 
Newborns Group B Streptococcus, S. pneumoniae, L. monocytogenes, E. coli
Babies and young children S. pneumoniae, N. meningitidis, H. influenzae type b (Hib), group B Streptococcus
Teens and young adults N. meningitidis, S. pneumoniae
Older adults S. pneumoniae, N. meningitidis, Hib, group B Streptococcus, L. monocytogenes

Types

Pneumococcal Meningitis 

Pneumococcal meningitis is the most common and serious form of bacterial meningitis. This type of meningitis can lead to neurological damage. Each year there are about 6,000 new cases in the United States.

Pneumococcal meningitis is caused by the bacteria Streptococcus pneumoniae. This type of bacteria is also responsible for bacterial pneumonia and ear and sinus infections. When it spreads to the bloodstream, it can lead to septicemia.

Groups most at risk of contracting pneumococcal meningitis are those with a compromised immune system or under two years of age. Fortunately, there is a vaccine available for some types of pneumococcal bacteria.

Meningococcal Meningitis

Meningococcal meningitis is caused by Neisseria meningitidis and accounts for 2,600 cases in the United States each year. It is highly contagious, especially for young infants and those living in dormitory settings such as college students.

This type of meningitis has a 10% to 15% death rate, and 10% to 15% of people who have this condition have permanent brain damage. Meningococcal meningitis is contagious, and it’s recommended that those living in close contact with someone who has it start prophylactic antibiotic therapy to be safe. 

Haemophilus Meningitis

A third type of bacterial meningitis caused by Haemophilus influenzae is now preventable with the Haemophilus influenzae b vaccine and is rare in the United States. Those most at risk are usually young children without access to the vaccine. 

Risk Factors

The risk factors for many types of bacterial meningitis are related to your risk of being exposed to the bacteria. Those living in close quarters with others or who work in a laboratory setting are at higher risk. 

Risk factors for bacterial meningitis include:

  • Age: It’s possible to be diagnosed with bacterial meningitis at any age, but infants, teens, and young adults are at higher risk. 
  • Living in community: Living in close quarters with others can put you at higher risk of being exposed to a bacterial infection and bacterial meningitis. Examples include adults living in institutional settings and young adults living on college campuses. 
  • Medical professionals: Those who work with sick individuals or in a lab setting may be more likely to be exposed to dangerous bacterial infections.
  • Immunocompromised individuals: Certain medical conditions like cancer can weaken one’s immune system and make you more susceptible to bacterial infections. If you have had your spleen removed or are currently taking corticosteroids, your risk is higher as well. 

Pregnant women are at increased risk of contracting listeriosis, a bacterial infection caused by the bacteria Listeria monocytogenes. This condition is usually mild in pregnant women, but can cause serious health problems in the fetus. L. monocytogenes are spread through contaminated food. Pregnant women can reduce their risk by avoiding certain foods during their pregnancy. 

Diagnosis

It’s important to see your doctor or go to the emergency room as soon as you suspect that you have bacterial meningitis. Your doctor will start by taking a history and performing a physical exam. They will examine your skin for a purple or red rash. Your doctor will also perform a range-of-motion test on your neck to see if it is stiff.

Possible diagnostic tests include:

During a spinal tap, your doctor will have you lie on your side with your knees pulled up to your chest if possible. They will then insert a thin needle between two of your vertebrae in the lower spine to remove spinal fluid and send it to the lab for testing.

Your doctor will also examine the fluid first. Cerebrospinal fluid should be clear, but may appear cloudy in those with bacterial meningitis. Your doctor may also recommend taking samples of your urine and mucus.  

Treatment

As soon as your doctor diagnoses you with meningitis, you will be admitted to the hospital to receive intravenous (IV) antibiotics. A corticosteroid is often prescribed to help bring down the swelling around your brain and spinal cord. This can reduce the chance of complications due to the swelling. 

Once your spinal tap reveals which type of bacteria is causing your meningitis, the medical team may switch to a more specific antibiotic that is effective against that bacteria. Treatment will also include IV nutrition as you may be dehydrated from not eating or if you have been vomiting. The length of the treatment will depend on the severity of your condition and how quickly your body responds to the medications. 

Bacterial meningitis can lead to shock in the body. During shock, your blood pressure drops, and many organs and your limbs do not receive adequate blood supply. Shock can quickly result in death, so it is crucial to seek emergency treatment as soon as you suspect you have bacterial meningitis. 

Prevention

The best prevention for several types of bacterial meningitis is vaccination. Vaccines can prevent some types of bacterial meningitis:

  • Meningococcal vaccines help protect against N. meningitidis
  • Pneumococcal vaccines help protect against S. pneumoniae
  • Hib vaccines help protect against Hib

Only the first of the three vaccines listed is specifically for meningitis. The other two are for bacterial infections that can sometimes, but usually don't, cause meningitis.

Vaccines don’t protect against every strain of bacteria, so it’s best to use caution and talk to your doctor if you believe you have been exposed. If someone in your household or dormitory has been diagnosed with bacterial meningitis, it’s possible that your doctor may recommend starting an antibiotic to protect you from contracting it as well. 

If you are pregnant, your doctor will check your blood for the bacteria group B Streptococcus before you give birth since it can be passed on to your newborn during childbirth and lead to bacterial meningitis. If your blood is positive for group B Strep, your baby will be protected when your medical team administers IV antibiotics during labor and before birth. If you have concerns about your test result, talk with your obstetrician. 

Pregnant women can help protect their babies from bacterial meningitis by avoiding foods that may carry L. monocytogenes, including:

  • Soft cheeses
  • Raw sprouts
  • Melons
  • Hotdogs and lunch meats 
  • Smoked fish
  • Unpasteurized milk 

Prognosis

Bacterial meningitis is a serious condition that can quickly become life-threatening. Early treatment is essential and may help reduce the chance of possible complications, such as:

Most people who receive treatment right away recover. The disease has a 10% death rate, so early intervention and treatment are crucial. 

Summary

Bacterial meningitis is contagious and potentially life-threatening. It's therefore important to avoid close contact with others and seek medical treatment right away if you have bacterial meningitis.

A Word From Verywell

Being diagnosed with bacterial meningitis is scary and may leave you feeling uncertain about the future. Remember that early intervention is important, and that most people who are treated early do recover. If you develop the classic symptoms of meningitis, such as a fever with a stiff neck, seek emergency treatment right away. The sooner your medical team administers IV antibiotics and a corticosteroid, the better you will be protected from possible complications. 

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