Bacterial meningitis

Meningitis is an inflammation of the central nervous system, specifically the membranes and fluid surrounding the brain and spinal cord. Bacterial meningitis is a medical emergency!


Causes/associated factors
As the name implies, bacterial meningitis is caused by a bacterial infection. Meningitis can have other causes, such as a viral or fungal infection. Viral meningitis is more common and usually less severe.
About two-thirds of the bacterial meningitis cases in the United States occur in children younger than age 5. Occurrence peaks between ages 6 months and 12 months, and tapers off from there. It's important to remember that bacterial meningitis can develop at any age, however, especially if you have a weak immune system.

Bacterial meningitis can develop after an infection elsewhere in the body if bacteria enters the bloodstream and travels to the membranes that surround the brain and spinal cord. Bacteria can also enter the bloodstream through a skin wound, head trauma, lumbar puncture (taking a sample of the fluid that surrounds the brain and spinal cord through a needle placed in the lower back), surgery or an anatomic abnormality. Sometimes, the infection spreads through contact with infected respiratory secretions coughed or sneezed into the air.

Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenza are responsible for most cases of meningitis from age 3 months to adulthood. Thanks to widespread vaccination against Haemophilus influenza type B, however, infections from this particular type of bacteria are decreasing.

Adult cases of bacterial meningitis are typically related to S. pneumoniae and N. meningitidis. Outbreaks typically occur where people live in congested quarters, such as college dorms or military barracks.

Meningococcal meningitis is a type of bacterial meningitis specifically caused by the N. meningitidis bacteria. Community outbreaks of meningococcal infections have been reported in the United States and Canada since 1990. This type of meningitis is most common in children younger than age 1. People ages 18 to 23 also have a slightly higher risk of infection. First-year college students have a modestly higher risk of infection compared to others in their age group, especially if they live in dormitories.

Bacterial meningitis in newborns up to age 3 months is usually caused by E. coli bacteria, although group B streptococcus is becoming an increasingly common cause.

Infants and young children, people who live in congested quarters and those who live with someone who has the infection are more susceptible to bacterial meningitis. Other risk factors include:

alcoholism
diabetes
cancer
having a weak immune system
having your spleen removed
taking certain medications after an organ transplant

Transmission
Some forms of bacterial meningitis are contagious, especially if you have close or prolonged contact with the infected person. The contagious period depends on the type of bacterium. In some cases, it's unknown. You may be contagious as long as the bacteria remain in your upper respiratory tract, however. With meningococcal or haemophilus meningitis, you're no longer infectious when the bacteria aren't detected in secretions from the back of your nose (usually after 24 to 48 hours of antibiotic medication).
The incubation period (time from exposure until symptoms appear) varies for each type of bacterium. For meningococcal meningitis, the incubation period is one to 10 days, but usually less than four days. The incubation period for haemophilus meningitis is unknown, but suspected to be two to four days.


Signs/symptoms
In most cases, bacterial meningitis is preceded by an upper respiratory infection, such as pneumonia or an ear or sinus infection. Symptoms usually appear suddenly (within hours), even when there's no preceding illness. At times, symptoms may develop over one to two days.
The classic symptoms of bacterial meningitis include a high fever, severe headache and stiff neck. Other symptoms may include:

chills
stiff back
nausea and vomiting
aversion to bright light
drowsiness, stupor or coma
changes in behavior (a child may become combative or depressed, for example)
confusion
seizures
pain in the abdomen, arms, legs or joints
a purplish or red rash that does not turn white when pressure is applied
sudden bruising
Because young children and elderly adults with other health problems can't always communicate easily, their symptoms may be harder to evaluate. Also, they may not have classic symptoms. You may notice:

irritability
unusual drowsiness, listlessness or prolonged sleepiness
aversion to bright light
appetite loss, vomiting, refusal to eat or weak sucking
seizures
weakness or loss of coordination
confusion or agitation
stiff neck (Young children may hold their necks stiffly, arch their heads back, or hesitate to bend their heads forward. Infants may not have these neck symptoms at all. Elderly adults may not have these symptoms either, especially if diabetes, cardiopulmonary disease or other debilitating diseases are present.)
fever (It's also possible that body temperature may be normal or below normal, however.)
Infants may have a change in tone of voice, skin color or breathing. For example, you may notice a high-pitched cry or persistent whine, jaundice (yellowing of the skin and whites of the eyes) or respiratory distress. Infants may also have diarrhea or vomiting. Some babies become more irritable or even inconsolable when being held.


Diagnosis
The doctor will review your medical history and do a physical exam of your head, eyes, ears, neck, chest, abdomen, nervous system and skin.
You may be asked to lie on your back while the doctor places his or her hands behind your neck and pushes your head forward. Meningitis may be suspected if this is painful or you're resistant.

Or, you may be asked to lie on your back while the doctor tries to flex your leg at the hip and the knee, and then straighten the knee. Meningitis may be suspected if this is painful or you're resistant.

A series of blood tests may be done, and any samples will be analyzed in the lab. A sample of cerebrospinal fluid (the fluid that surrounds the brain and spinal cord) may be taken with a procedure called a lumbar puncture or spinal tap, in which a needle is placed in your lower back. The fluid will be studied or cultured for cell count and type, glucose (sugar) level, bacteria and protein count. Viral and fungal cultures and other studies may be done as well. If the diagnosis isn't clear, another test called a polymerase chain reaction can be done.

Imaging studies such as X-rays or computed tomography (CT scan, a computer-generated, cross-sectional picture of internal body parts) may be done to determine whether there's increased pressure on your brain or any abscesses (collections of pus) have developed in your chest, skull, sinuses or brain.


Treatment
If bacterial meningitis is suspected, you'll receive antibiotics as soon as possible -- even before the results of diagnostic tests are complete. The specific antibiotic will depend on the type of bacterium causing the infection. A type of penicillin is often the antibiotic of choice, especially for older patients. It's usually given intravenously (into a vein) or intrathecally (into the spinal canal) to help maintain an appropriate concentration in the bloodstream. If the strain of bacteria in your system is resistant to penicillin or you have a penicillin allergy, you may need another antibiotic or a combination of antibiotics.
Depending on the specific bacterium, intravenous antibiotics are usually needed for at least 10 to 14 days. Your doctor may also prescribe steroids, bedrest and intravenous fluids to prevent dehydration. If your mastoids (the round bone behind each ear) or sinuses are infected, they may need to be drained surgically.

Remember, bacterial meningitis is a medical emergency. If you suspect meningitis, seek medical attention immediately.


Complications
Bacterial meningitis can lead to serious long-term complications, including:
hearing loss
visual impairment
seizures
behavioral problems or personality changes
developmental delays or speech defects
mental retardation
paralysis
stroke (a condition caused by a lack of blood flow to a part of the brain)
coma
It's also possible to develop recurrent meningitis. In this case, you'll need additional evaluation to determine if an anatomical defect is allowing bacteria to enter your central nervous system. In severe cases, complications of bacterial meningitis can be rapidly fatal.


Pregnancy-specific information
Pregnancy doesn't increase the risk of developing bacterial meningitis. If you've been exposed to the infection, consult your doctor. Preventive measures may differ from those recommended for other adults.
About one-third of pregnant women have group B streptococcus (GBS) bacteria in the birth canal or rectum. GBS can spread to the baby before or during birth and cause serious illness -- including bacterial meningitis. GBS is the most frequent cause of ife-threatening infections in newborns.

The U.S. Centers for Disease Control and Prevention (CDC) recommends screening all pregnant women for GBS. Typically, tissue samples are swabbed from the mother's vagina and rectum between the 35th and 37th week of pregnancy.

If you have a known or suspected infection with GBS, you'll be given intravenous antibiotics during labor and delivery to help prevent infection in your baby.


Senior-specific information
Again, the symptoms of meningitis may vary in elderly adults.

Prevention
To prevent infection, wash your hands thoroughly and often. Also, dispose of tissues properly. Contact your doctor immediately if you have close contact with someone who has bacterial meningitis, including:
child care workers
family members
household contacts
dormmates
classmates
anyone who may have had contact with an infected person's saliva (through sharing eating utensils or kissing, for example)
If you were exposed to meningococcal meningitis, the doctor may recommend preventive antibiotic treatment with rifampin, ciprofloxacin or rocephin.

If there's a community outbreak of meningococcal meningitis, your doctor may recommend being vaccinated. The meningococcal vaccine is usually given to those older than age 2 for protection from four strains of N. meningitidis bacteria (A, C, Y and W135). The protection takes effect seven to 10 days after the vaccination. Of course, the vaccine won't be useful if the outbreak is caused by a different strain of N. meningitidis. The vaccine remains effective for about three years.

Routine vaccination against meningococcal meningitis is recommended if you have certain medical conditions that affect the immune system, your spleen isn't functioning properly, or you work in a lab where you may be exposed to the bacteria in the air. Since the routine vaccination of military recruits in the United States, the frequency of meningitis among military personnel has decreased substantially. The vaccine is also recommended for first-year college students who want to decrease the risk of meningitis.

Routine childhood immunization with the Haemophilus influenzae type B (Hib) vaccine has reduced the occurrence of bacterial meningitis related to H. influenzae by about 95 percent. For adequate immunity, it's important to complete the full series of shots. The CDC recommends that a susceptible (unimmunized or incompletely immunized) child younger than age 4 who is exposed to someone with haemophilus meningitis receive preventive treatment with rifampin as soon as possible. The CDC also recommends rifampin treatment for any household contacts or adults who've been in close contact with the exposed child. Before treating all contacts with rifampin in a child care setting, however, the CDC recommends determining how many cases have occurred, how many children aren't fully immunized and the length of exposure.

A pneumococcal vaccine is also available to help prevent meningitis caused by S. pneumoniae bacteria, as well as other diseases caused by this type of bacteria.