What Are the Signs and Symptoms of Bacterial Meningitis?

Meningitis is an inflammation of the membranes that surround the brain and spinal cord (meninges). It can be caused by bacterial, fungal, viral, or parasitic infection. When meningitis is caused by bacterial infection, it is called bacterial meningitis.

Three layers of membranes or meninges surround and protect the brain and spinal cord.

• Outer tough layer (dura mater)
• Web-like middle layer (arachnoid mater)
• Innermost layer that closely follows the contours of the brain (pia mater)

In addition to protecting the brain and spinal cord, the meninges support the blood vessels and provide a continuous channel for the flow of cerebrospinal fluid.

Bacterial meningitis may begin as a cold-like illness that progresses to frank meningitis (with symptoms such as high fever, neck stiffness, vomiting, and seizures). The bacteria generally infect the respiratory tract and then travel to the meninges via the bloodstream. Direct infection of the meninges may occur, such as after a skull fracture, sinus infection, and, rarely, after a brain or spine surgery. 

Bacterial meningitis is a serious disease that may cause complications such as stroke, hearing loss, vision loss, brain damage, and even death if not timely treated.

Various bacteria can cause bacterial meningitis, the most common being meningococcal and pneumococcal bacteria.

1. Streptococcus pneumoniae

Meningitis caused by Streptococcus pneumoniae (pneumococcus) is called pneumococcal meningitis and is the most common form of meningitis, accounting for about 6,000 cases each year in the United States. 

Pneumococcal meningitis is the most serious variety of bacterial meningitis with a risk of complications, such as hearing loss and brain damage. Fortunately, safe and effective vaccines are available to protect against certain pneumococcal strains. 

Besides meningitis, Streptococcus pneumoniae causes other diseases, including pneumonia, sinus and ear infections, and septicemia (blood poisoning). People who are immunocompromised (such as patients with human immunodeficiency virus, organ transplant and cancer) and children under the age of 2 are particularly at risk.

2. Neisseria meningitidis (meningococcus)

Meningococcus bacteria cause a type of meningitis called meningococcal meningitis, which is another common form of meningitis accounting for about 2,600 cases each year in the United States. 

Meningococcal meningitis is a highly infectious disease, particularly affecting immunocompromised infants and adults. The risk is high in people traveling to places where meningococcal infections are endemic. Military recruits and people residing in dormitories also have a high risk. Due to its high infectivity, close contacts of a person diagnosed with meningococcal meningitis are administered prophylactic (preventive) antibiotics. 

Like pneumococcal meningitis, meningococcal meningitis can cause serious disease, leading to death in about 10%-15% of cases. Affected people have a 10%-15% of developing serious complications such as brain damage.

3. Haemophilus influenzae

Previously one of the most common forms of meningitis (particularly in children under age 5), Haemophilus influenzae meningitis cases have declined due to the widespread use of the Haemophilus influenzae b vaccine in the United States. The disease is particularly seen in immunocompromised individuals, unvaccinated children, and people in child-care settings.

4. Listeria monocytogenes

Meningitis caused by listeria is particularly seen in pregnant women and immunocompromised individuals. The infection generally occurs upon consuming contaminated foods such as raw vegetables, deli meats, hot dogs, and foods made with unpasteurized milk.

5. Escherichia coli (E coli)

Some strains of E coli (such as E coli K1) may cause meningitis particularly in newborns (especially premature and low birth weight babies) and elderly individuals. Newborns typically get the infection through the mother’s birth canal. People with a cerebrospinal fluid shunt (a device to relieve excessive pressure around the brain) are also at risk of getting E coli meningitis.

6. Mycobacterium tuberculosis

Meningitis caused by mycobacterium is called tuberculous meningitis, which is typically seen in people who have or had tuberculosis. The infection is generally seen in developing countries where tuberculosis is common.

Diagnosis of bacterial meningitis involves taking a detailed medical history, performing a physical examination (particularly neurological examination), and ordering certain tests.

Tests used to diagnose bacterial meningitis include:

• Blood tests
• Urine tests
• Cerebrospinal fluid exam
• Computed tomography scan
• Magnetic resonance imaging
• Electroencephalography

Appropriate antibiotics to target the particular bacteria are the first line of treatment. Because the passage of substances, including medications, is limited from the blood to the brain via a layer of specialized cells (blood-brain barrier), antibiotics that cross the blood-brain barrier are used to treat bacterial meningitis.

Medications may also be prescribed to treat fever, pain, seizures, vomiting, and other symptoms. Patients are generally hospitalized where an intravenous line may be established to administer medications and correct fluid and electrolyte imbalances. Steroid medications may be administered to reduce inflammation and prevent complications such as hearing loss.