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).

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.

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

Risk factors in adults and children include recent brain surgery and recent injury to the head. The infection is sometimes connected to spinal fluid shunt placement after brain surgery. Spinal abnormalities, urinary tract abnormalities, a local infection, or urinary tract infection may make children vulnerable to this type of meningitis.

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

For any patient with meningitis, it is important to perform a lumbar puncture (spinal tap). In a lumbar puncture, doctors take a sample of the patient's spinal fluid (known as cerebrospinal fluid, or CSF) for testing.

• 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)