Comparison of Bacterial and Viral Meningitis

Inflammation of the Brain's Meninges Caused by Bacteria and Viruses

Apr 14, 2009

Meningitis is an inflammation of the meninges that line and protect the brain and spinal cord. It occurs when bacteria or viruses breech the blood-brain barrier.

Meningitis infection results when microorganisms that have entered the body travel through the blood, and contaminate the cerebral spinal fluid. Microbes in the blood stream can be fought off by the body’s white blood cells. However, there are no white blood cells in the cerebral spinal fluid to combat infection.

During infection, the immune system sends out chemical signals that result in inflammation, an immune response that normally speeds healing. However, in the CNS, inflammation causes swelling and increased pressure inside the skull, which interferes with the brain's normal functioning.

General Symptoms of Meningitis

Some of the symptoms of bacterial and viral meningitis are similar, although bacterial meningitis is more severe and dangerous. Adults and older children with meningitis typically experience:

Causes of Bacterial Meningitis

Bacterial meningitis can be severe, possibly result in brain damage, loss of hearing, and even death. Several types of bacteria can cause meningitis, but meningococcal and pneumococcal represent the majority of cases.

Meningococcal meningitis is caused by the Gram-negative bacterium Neisseria meningitidis, and accounts for more than 50% of all cases of bacterial meningitis in the U.S, affecting mostly adults and young adults. N. meningitidis strain B accounts for about three quarters of all meningococcal cases and has the highest fatality rate. An additional symptom, specific to meningococcal meningitis, is a distinctive rash, indicative of septicemia (bacteria in the blood).

Pneumococcal meningitis is caused by the Gram positive bacterium Streptococcus pneumoniae. Newborns and infants are at highest risk of contracting this type of meningitis. The fatality rate is about 20%, and those that survive have a higher incidence of brain damage than is typical in other forms of the disease.

Haemophilus influenzae, a Gram-negative bacterium, is a third cause of bacterial meningitis and, prior to availability of the vaccine, was once a common, deadly childhood illness.

Causes of Viral Meningitis

Meningitis caused by viruses is typically less severe and will often resolve without specific treatment. Many viruses can cause meningitis, including enteroviruses, herpes viruses, mumps virus, HIV, and lymphocytic choriomeningitis virus (LCMV).

Diagnosis, Treatment, and Prevention of Meningitis

In addition to observing the general symptoms of meningitis, a lumbar puncture may be required to confirm the condition. A needle is inserted into the spinal canal to extract a sample of cerebrospinal fluid (CFS), which is then examined in a medical laboratory to determine the type of pathogen.

Because bacteria and viruses are different types of infectious particles that reproduce in distinct ways, the treatments for bacterial and viral meningitis are not the same.

In cases of bacterial meningitis, prompt administration of appropriate antibiotics is required; antibiotics with action against Gram-positive, -negative or broad-spectrum, depending on the pathogen. Corticosteroid drugs may also be used to reduce inflammation.

Viral meningitis may require no treatment at all, or may be treated with antiviral drugs (drugs that interfere with replication of the virus causing the meningitis) and corticosteroids.

Some forms of meningitis (such as those caused by Neisseria meningitidis, Haemophilus influenzae type B, Streptococcus pneumoniae or mumps virus infections) can be prevented by immunization.

If you suspect that you or a loved one may have meningitis, immediately seek help from a medical professional.

Sources

The copyright of the article Comparison of Bacterial and Viral Meningitis in Human Infections is owned by Tami Port. Permission to republish Comparison of Bacterial and Viral Meningitis in print or online must be granted by the author in writing.