Meningitis - gram-negative

Alternative names
Gram-negative meningitis

Gram-negative meningitis is an infection of the membranes covering the brain and spinal cord (meninges) caused by gram-negative bacteria (bacteria that turn pink when exposed to a special stain).

Causes, incidence, and risk factors

The most common causes of meningitis are bacterial infections that start in other parts of the body and spread to the brain or spinal cord via the bloodstream. Meningitis can also also caused by viruses, chemical irritation, or tumors.

Acute bacterial meningitis, which can be caused by gram-negative bacteria, is very serious and should be treated immediately to prevent permanent damage. Bacteria causing gram-negative meningitis include Pseudomonas aeruginosa, Escherichia coli, Enterobacter aerogenes, Proteus morganii, and Klebsiella pneumoniae.

Risk factors include recent brain surgery and recent trauma or injury to the head. The infection is sometimes associated with spinal fluid shunt placement after brain surgery. Spinal abnormalities, urinary tract abnormalities, a local infection, or urinary tract infection may be predispose children to this type of meningitis.

Gram-negative meningitis is much more common in infants than adults.


  • Fever  
  • Severe headache  
  • Nausea and vomiting  
  • Stiff neck  
  • Sensitivity to light (photophobia)  
  • Mental status changes  
  • Symptoms suggesting infection of bladder or kidney, intestines, or lung that might be the source of the spinal fluid infection

Signs and tests

  • Low blood pressure  
  • Fast heart rate  
  • Stiff neck  
  • Elevated white blood cell count in blood  
  • Spinal fluid showing increased white blood cells, low glucose, high protein  
  • Special stain of the spinal fluid showing white blood cells and sometimes gram-negative bacteria  
  • CSF culture growing gram-negative bacteria  
  • Blood culture growing gram-negative bacteria  
  • CT scan of the brain (usually normal)

It is important to recognize the symptoms of this kind of meningitis and seek treatment as soon as possible to prevent serious illness or death. Antibiotic medication through an IV is usually started right away.

Expectations (prognosis)
Many people recover completely, but a large number of people suffer permanent neurologic damage or die from this type of meningitis. Between 40% and 80% of patients with gram-negative meningitis do not survive. The likelihood of survival depends on the patient’s age and other medical conditions and how quickly the infection is treated.


  • Shock with damage to other organs  
  • Brain abscess (collection of bacteria in the brain itself)  
  • Brain damage

Calling your health care provider
Go to the emergency room or call the local emergency number (such as 911) if you notice symptoms that indicate meningitis. This condition can be very serious and needs immediate treatment.

Prompt treatment of related infections may reduce the risk of meningitis.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.