Gram-Negative Meningitis

Written by Brian Krans | Published on September 18, 2012
Medically Reviewed by George Krucik, MD

What Is Gram-Negative Meningitis?

Gram-negative meningitis is a type of infection of the membrane that surrounds the brain and spinal cord.

“Gram-negative” meningitis refers to Gram staining, a routine laboratory test that determines the presence of microorganisms like bacteria or fungi in blood or tissue.

During the test, the Gram stain will turn pink if Gram-negative bacteria are present. These types of bacteria can also cause infections and pneumonia.

According to the Centers for Disease Control and Prevention, Gram-negative bacteria are resistant to multiple antibiotic drugs commonly used to treat infection. In addition, they have the capability to become resistant to new drugs (CDC, 2011). As a result, Gram-negative meningitis is harder to treat than other forms of meningitis. According to Emory Family Health, an estimated 40 to 80 percent of Gram-negative meningitis cases end in death (Yost, 2012).

It is more common in infants than adults.

What Causes Gram-Negative Meningitis?

Gram-negative meningitis occurs when the membrane of the brain and spinal cord becomes infected with a strain of Gram-negative bacteria. These include:

  • Acinetobacter baumannii
  • Enterobacter aerogenes
  • Escherichia coli (E. coli)
  • Klebsiella pneumoniae
  • Pseudomonas aeruginosa (NIH, 2010)

Risks of Catching Gram-Negative Meningitis

Gram-negative bacteria don’t reach the brain or spinal column easily. Both parts of the body are generally well-protected from outside invaders. However, certain medical events increase the chances of getting any kind of meningitis. Examples of these events include:

  • brain surgery
  • injury to the brain or head
  • spinal abnormalities, such as spina bifida
  • spinal fluid shunt after brain surgery (used to relieve swelling)
  • urinary tract abnormalities, such as urinary tract infection (UTI) with septicemia
  • weakened immune system

What Are the Symptoms of Gram-Negative Meningitis?

Meningitis is often mistaken for the flu because early signs are similar. Additionally, both develop over a period of several hours to a few days.

Symptoms of Gram-negative meningitis in adults include:

  • confusion
  • high fever
  • lack of interest in eating or drinking
  • nausea
  • seizures
  • sensitivity to light
  • severe headache
  • sleepiness
  • stiff neck
  • vomiting

Symptoms of meningitis in newborns and infants include:

  • bulge in the soft spot on the top of the head
  • constant crying
  • excessive irritability
  • excessive sleepiness
  • inactivity
  • poor feeding
  • seizures
  • sluggishness
  • stiffness in the body and neck

How Is Gram-Negative Meningitis Diagnosed?

Doctors start with a physical exam. Your doctor will look for signs of a fast heart rate, fever, and stiff neck. He or she will also check if you’re confused or disorientated.

If your doctor suspects meningitis, he or she will order a spinal tap (also known as a lumbar puncture). During this procedure, a needle will be used to extract cerebrospinal fluid, the clear liquid that cushions your brain and spinal column.

The fluid is sent to a laboratory where it is tested. People with meningitis often show low levels of sugars, but increased levels of proteins and white blood cells.

The fluid will also be tested with a Gram stain test. In addition to a positive or negative result, the test will provide a description of the bacteria involved in the infection. This helps guide treatment.

Results can take up to a week to return from the laboratory. In the meantime, your doctor may order other tests to help reach a definitive diagnosis.

Additional tests for meningitis include:

  • blood culture
  • computed tomography (CT) scan
  • polymerase chain reaction (PCR) amplification, used to amplify DNA
  • X-ray

How Do Doctors Treat Gram-Negative Meningitis?

Antibiotics will be started as soon as meningitis is diagnosed. Most other types of meningitis respond to normal antibiotics. However, several different drugs must used to treat Gram-negative meningitis, since it is typically resistant to normal antibiotics. Ceftazidime is one of the most common types. Other antibiotics may be used as well.

Your doctor will also prescribe painkillers or other necessary medications to treat problematic symptoms.

If your infection was caused by a shunt after brain surgery, the shunt may be removed to prevent further infection.

Recovering from Gram-Negative Meningitis

Gram-negative meningitis is the most difficult type of meningitis to treat. According to the National Institutes of Health, as high as 80 percent of patients do not survive (NIH, 2010). Survival rate depends on:

  • age (newborns, infants, and the elderly are at the highest risk)
  • how quickly treatment begins
  • complications from other conditions, such as brain damage

A full recovery is possible. However, many people have permanent brain damage after having Gram-negative meningitis.

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