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

Gram-negative meningitis

Acute bacterial meningitis can be caused by Gram-negative bacteria.

Meningococcal and H. influenzae meningitis are due to Gram-negative bacteria and are covered in detail in other articles. This article covers bacteria causing Gram-negative meningitis due to the following common causes:

•  Escherichia coli
• Klebsiella pneumoniae
• Pseudomonas aeruginosa
• Serratia marsescens

Gram-negative meningitis is more common in infants than adults, but is of growing importance in adults, especially those with one or more risk factors. 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
• Weakened immune system

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

Other symptoms that can occur with this disease:

• Agitation
• Bulging fontanelles in infants
• Decreased consciousness
• Poor feeding or irritability in children
• Rapid breathing
• Unusual posture, with the head and neck arched backwards (opisthotonos)

The doctor or nurse will examine you. This will usually show:

• Fast heart rate
• Fever
• Mental status changes
• Stiff neck

If the health care provider thinks you may have meningitis, a lumbar puncture (spinal tap) should be done to remove a sample of spinal fluid (cerebrospinal fluid, or CSF) for testing.

Other tests that may be done include:

• Blood culture
• Chest x-ray
• CT scan of the head

This list is not all-inclusive. 

Antibiotics should be started as soon as possible. Ceftriaxone, ceftazidime, or cefepime are the most commonly used antibiotics for this type of meningitis. Other antibiotics may be used, depending on the type of bacteria.

If you have a spinal shunt, it may be removed.

The early treatment is started, the better the outcome. 

Many people recover completely, but a large number of people have permanent brain damage or die from this type of meningitis. Young children and adults over age 50 have the highest risk of death. How well you do depends on:

• Age
• How quickly the infection is treated
• Overall health

• Brain damage
• Buildup of fluid between the skull and brain (subdural effusion)
• Hearing loss
• Hydrocephalus
• Seizures

Call the local emergency number (such as 911) or go to an emergency room if you suspect meningitis in a young child who has the following symptoms:

• Feeding problems
• High-pitched cry
• Irritability
• Persistent unexplained fever

Call the local emergency number if you develop any of the serious symptoms listed above. Meningitis can quickly become a life-threatening illness.

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

Swartz MN. Meningitis: bacterial, viral, and other. In:Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 360.

Tunkel AR, Van de Beek D, Scheld WM. Acute meningitis. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 84.

Thigpen MC, Whitney CG, Messonnier NE, et al. Emerging Infections Programs Network. Bacterial meningitis in the United States, 1998-2007. N Engl J Med. 2011 May 26;364(21):2016-25.