Bacterial meningitis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 29, 2016
StartDiseasesBacterial meningitis

Bacterial meningitis is a form of meningitis caused by a bacterial infection. While not everyone who develops bacterial meningitis becomes seriously ill, it can be fatal or cause chronic complications such as brain damage and intellectual disability if left untreated. Less common but more severe than viral forms of the disease, bacterial meningitis requires prompt medical treatment as it is a serious condition.

Contents

Definition & Facts

Meningitis comes in three forms: fungal meningitis, bacterial meningitis, and viral meningitis. Of these three forms, viral meningitis is the most common. According to the Centers for Disease Control or CDC, bacterial meningitis is caused by a variety of bacteria, but the most common are group B Streptococcus, Listeria monocytogenes and Streptococcus pneumoniae

Meningitis is inflammation of the meninges which are the protective membranes covering the brain and the spinal cord. They include three layers: the pia mater (inner layer), arachnoid mater, and dura mater (outer layer). This condition killed about 500 Americans each year between 2003 and 2007 according to the Centers for Disease Control and Prevention.

Symptoms & Complaints

People who contract bacterial meningitis exhibit certain symptoms soon after infection. Some of the most common symptoms in teenagers and adults include:

It is much more difficult to determine the symptoms of bacterial meningitis in babies. Infants may have symptoms such as:

Bacterial meningitis can escalate rapidly. Many people develop symptoms within three to seven days after infection but others experience symptoms within 24 hours. 

Causes

Coming into contact with certain bacteria is the cause of bacterial meningitis. Types of bacteria and the respective infections they cause include group B streptococcus (group B streptococcal infection), Neisseria meningitidis (meningococcal meningitis, a form of meningococcal disease), Haemophilus influenzae,

Many of these types of bacteria live in the environment and do not always cause illness. In addition, this bacteria can also exist within the human body in the respiratory tract or nasal passages without causing illness or symptoms.

Doctors do not know exactly why certain people develop this dangerous condition, but there are factors that can increase one's risk. Babies, for example, are at higher risk than other populations. People who travel to sub-Saharan may be at greater risk. Those who live together in large groups such as students who live on a college campus are more prone to developing bacterial meningitis. People with a weakened immune system, those who abuse alcohol, or those who suffer from a traumatic brain injury are also at an increased risk.

Most forms of bacterial meningitis are significantly less contagious than viral meningitis. Nevertheless, they can be spread through contact with an infected person's saliva such as that which occurs during kissing.

Diagnosis & Tests

Prompt diagnosis is the key to treating bacterial meningitis successfully. Doctors will ask about the patient's family history and medical history and take a physical examination. They will typically use laboratory tests when diagnosing this condition. Blood tests may reveal the presence of bacteria.

The most reliable diagnostic exam is the spinal tap (lumbar puncture) which can confirm the diagnosis. This procedure involves obtaining a sample of cerebrospinal fluid by removing it through fine-needle aspiration . The presence of bacteria in this fluid indicates bacterial meningitis is the cause of illness. This method also allows doctors to determine if the cause of meningitis is viral, bacterial or fungal.

It may be necessary for the physician to order various medical imaging studies such as magnetic resonance imaging (MRI)s or computed tomography (CT) scans to rule out other conditions and/or monitor possible complications like hydrocephalus and brain abscess. These imaging studies are typically not helpful in diagnosing acute cases of bacterial meningitis, and lumbar punctures are preferable.

Treatment & Therapy

Doctors use powerful antibiotics to treat bacterial meningitis. These antibiotics may be delivered intravenously. In addition, they may also use corticosteroids to reduce inflammation in the brain. Doctors may also administer IV fluids in order to replenish fluids and nutrients lost during bouts of vomiting and high fever. 

If prompt diagnosis is not made, the prognosis may be deadly. Approximately 10 percent of those who contract this illness die from the infection. When treatment is not begun quickly enough, there is a higher chance of lasting effects from the infection such as cognitive deficits or paralysis.

Prevention & Prophylaxis

While it is not always possible to prevent bacterial meningitis, there are ways to reduce the risks. Vaccines are available for certain types of bacterial meningitis. These vaccines have been effective against Streptococcus pneumoniae (pneumococcal vaccine), Haemophilus influenzae type b (Hib vaccine), and Neisseria meningitidis (meningococcal vaccine). While these may not completely eliminate the chance of developing bacterial meningitis, they can reduce it. These vaccines are recommended for anyone who:

  • Travels outside the U.S on a regular basis
  • Lives in college dorms
  • Is in the military
  • Is exposed to causal bacteria at work
  • Has a weakened immune system

Not everyone is a good candidate for vaccination against this condition. Doctors do not recommend vaccination for anyone who has had a reaction to a meningitis vaccine in the past. People who have had serious or life-threatening reactions to any vaccine in the past should discuss it with their doctor before being vaccinated. Caution should be used when vaccinating pregnancy women and those who are sick. 

Doctors usually recommend preventative treatment to those who have been exposed to bacterial meningitis. This includes a round of preventative antibiotics for those who have close contact with an infected person. If possible, it is always best to avoid coming into contact with anyone who has a known bacterial meningitis infection.

Since babies are at an increased risk of developing bacterial meningitis, it is important to avoid exposing them to anyone who is sick. Parents and regular caregivers should be vaccinated against meningitis, since they can spread the illness to their babies. 

Staying as healthy as possible is the best way to avoid contracting bacterial meningitis or other serious diseases. This can be done by eating a healthy diet, exercising regularly, and getting adequate sleep. Consuming alcohol in moderation and avoiding cigarettes either by quitting smoking or never starting to begin with are also important factors in overall health.