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

See also:

• Aseptic meningitis
• Meningitis - cryptococcal
• Meningitis - H. influenzae
• Meningitis - meningococcal
• Meningitis - pneumococcal
• Meningitis - staphylococcal
• Meningitis - tuberculous

Acute bacterial meningitis can be caused by gram-negative bacteria. Bacteria causing gram-negative meningitis include:

• Acinetobacter baumannii
• Enterobacter aerogenes
• Escherichia coli
• Klebsiella pneumoniae
• Pseudomonas aeruginosa

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

Risk factors in adults and children include:

• Local infection
• Recent brain surgery
• Recent injury to the head
• Spinal abnormalities
• Spinal fluid shunt placement after brain surgery
• Urinary tract abnormalities
• Urinary tract infection

• Fever
• Mental status changes
• Nausea and vomiting
• Sensitivity to light (photophobia)
• Severe headache
• Stiff neck
• Symptoms of a bladder, kidney, intestine, or lung infection

A physical examination may show:

• Fast heart rate
• Low blood pressure
• Stiff neck

For any patient with meningitis, it is important to perform a lumbar puncture ("spinal tap"), in which spinal fluid (known as cerebrospinal fluid, or CSF) is collected for testing.

Tests include:

• Blood culture
• CSF culture
• CT scan of the brain
• White blood cell count
• Spinal fluid tests for white blood cells, glucose, protein
• Special stain of the spinal fluid

Antibiotic treatment through a vein (IV) usually starts right away. If you have a shunt, it may be removed to get rid of the infection.

It is important to recognize the symptoms of this meningitis, and seek treatment as soon as possible. Early treatment may prevent serious illness or death.

Many people recover completely, but a large number of people have permanent brain damage or die from this type of meningitis. Between 40% and 80% of patients with gram-negative meningitis do not survive, although these numbers may be improving. The likelihood of survival depends on:

• How quickly the infection is treated
• Other medical conditions that may be present
• The patient's age

• Brain abscess
• Brain damage
• Seizures
• Shock with organ damage

Go to the emergency room or call the local emergency number (such as 911) if you notice symptoms of meningitis. This condition can be very serious and needs immediate treatment.

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

Gram-negative meningitis

Swartz MN. Meningitis: bacterial, viral, and other. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 437.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.