Bacterial meningitis is a life-threatening infection of the membranes that cover the brain. It can be caused by any of several types of bacteria. The list of most common types has shifted over time, due to the impact of childhood and adult vaccines.
What is going on in the body?
The organisms responsible for bacterial meningitis generally begin growing in a person's nose and throat. If not stopped by the immune system, the bacteria go on to enter the bloodstream and travel to the central nervous system. The organisms then multiply in the fluid and the membranes around the brain.
The body's immune system responds with an outpouring of inflammatory cells and chemicals that are, in turn, responsible for many of the symptoms of meningitis. Inflammation may also play a role in some of the complications.
What are the causes and risks of the infection?
Bacterial meningitis is caused by bacteria that usually enter the body through the person's nose or throat. The bacteria can be transmitted to newborns during labor and delivery. Many people can have the bacteria in their noses or throats without developing meningitis.
Some bacteria are more likely to cause meningitis in very young infants, while others are seen more commonly in young adults. However, a person can contract meningitis at any age. People with a weakened immune system, such as those with AIDS, are also at high risk.
What can be done to prevent the infection?
Several types of bacterial meningitis are preventable by vaccines.
For instance, the vaccine against Hemophilus influenzae type B or Hib(not to be confused with influenza, which is a virus) is extremely effective. This vaccine, recommended routinely for children, has made Hib, once a common cause of meningitis in children, now almost nonexistent.
Similarly, pneumococcal vaccine, also a routinely recommended immunization, has dramatically reduced the incidence of meningitis and other serious infections due to pneumococci bacteria in infants.
More recently, an improved vaccine against meningococcal meningitis was licensed and recommended for teenagers and for college students living in dormitories. It is hoped that this vaccine will have the same impact on its target population group as have the Hib and pneumococcal shots.
For an individual exposed to someone with bacterial meningitis, antibiotics may be given for a few days to prevent an infection. Vaccination is considered more effective than the use of antibiotics for controlling an outbreak of meningococcal disease.
How is the infection diagnosed?
A person with bacterial meningitis will usually have become ill quite rapidly, with non-specific malaise, fever, and perhaps nausea and vomiting at first. The classical symptoms of very high fever and stiff neck may or may not be present.
On physical examination, the healthcare professional may find a temperature of 104 degrees Fahrenheit (40 degrees C) or higher, and may see tiny petechiae, or ruptured blood vessels, in the skin.
The diagnosis is confirmed with an examination of spinal fluid, the clear fluid surrounding the brain and spinal cord. This fluid is carefully drawn out using a thin needle inserted through the skin of the back into the spinal canal between the vertebrae.
The fluid is sent to the lab for examination. White blood cells, not normally found in spinal fluid, usually make the fluid cloudy in a person with bacterial meningitis.
Bacteria can often be grown in the lab from a sample of the fluid. This shows which bacteria are causing the infection, and which antibiotics will best treat it.
Chemical signs of the bacteria, called antigens, can sometimes be found in the spinal fluid. These are helpful for diagnosing the infection if for some reason the bacteria will not grow in the lab.
Long Term Effects
What are the long-term effects of the infection?
Bacterial meningitis can sometimes be fatal. Other long-term effects include hearing impairments; hydrocephalus, or fluid on the brain; brain damage; and loss of limbs.
What are the risks to others?
Bacterial meningitis is contagious. It can be transmitted to others through saliva or nasal secretions. The infection can be spread by kissing, as well as by sharing drinks, lip balm, lipstick, or cigarettes.
Those who have had close contact with a person with bacterial meningitis, including those giving medical care face to face, should talk to a healthcare professional about taking a course of antibiotics to keep from becoming infected themselves.
What are the treatments for the infection?
Bacterial meningitis may be treated with the following medications:
antibiotics, such as ampicillin (i.e., Principen), tobramycin (i.e., Tobrex), cefotaxime (i.e., Claforan), ceftriaxone (i.e., Rocephin), aztreonam (i.e., Azactam), ciprofloxacin (i.e., Cipro), meropenem (i.e., Merrem)
corticosteroids, such as methylprednisolone (i.e., Medrol), dexamethasone (i.e., Decadron) or prednisone, to decrease swelling in the brain
surgery to remove a brain abscess, or collection of pus
a ventilator, if breathing is impaired
What are the side effects of the treatments?
Antibiotics may cause stomach upset, rash, or allergic reactions. Corticosteroids can increase a person's risk of infection. Surgery may be complicated by bleeding, infection, or an allergic reaction to the anesthetic.
What happens after treatment for the infection?
Once bacterial meningitis is treated effectively, the person can return to normal activities.
How is the infection monitored?
Any new or worsening symptoms should be reported to the healthcare professional.