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Gram-negative meningitis

Meningitis is present when the membranes covering the brain and spinal cord become swollen and inflamed. This covering is called the meninges.

Bacteria are one type of germ that may cause meningitis. Gram-negative bacteria are a type of bacteria that behave in a similar manner in the body. They are called gram-negative because they turn pink when tested in the laboratory with a special stain called Gram stain.

Causes

Acute bacterial meningitis can be caused by different Gram-negative bacteria including meningococcus and H influenzae.

This article covers Gram-negative meningitis caused by the following bacteria:

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

Gram-negative meningitis is more common in infants than adults. But it can also occur in adults, especially those with one or more risk factors. Risk factors in adults and children include:

  • Infection (especially in the abdomen or urinary tract)
  • 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

Symptoms

Symptoms usually come on quickly, and may include:

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)

Exams and Tests

The health care provider will perform a physical exam. Questions will focus on symptoms and possible exposure to someone who might have the same symptoms, such as a stiff neck and fever.

If the provider thinks meningitis is possible, a lumbar puncture (spinal tap) will likely be done to remove a sample of spinal fluid for testing.

Other tests that may be done include:

Treatment

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

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

Outlook (Prognosis)

The earlier treatment is started, the better the outcome.

Many people recover completely. But, many people have permanent brain damage or die of this type of meningitis. Young children and adults over age 50 have the higher risk for death. How well you do depends on:

  • Your age
  • How soon treatment is started
  • Your overall health

Possible Complications

Long-term complications may include:

  • Brain damage
  • Buildup of fluid between the skull and brain (subdural effusion)
  • Buildup of fluid inside the skull that leads to brain swelling (hydrocephalus)
  • Hearing loss
  • Seizures

When to Contact a Medical Professional

Call 911 or the local emergency number 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

Meningitis can quickly become a life-threatening illness.

Prevention

Prompt treatment of related infections may reduce the severity and complications of meningitis.

Open References

References

Centers for Disease Control and Prevention website. Meningitis. About bacterial meningitis. www.cdc.gov/meningitis/about/bacterial-meningitis.html. Updated January 9, 2024. Accessed June 17, 2024.

Nath A. Meningitis: bacterial, viral, and other. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 384.

Hasbun R, Van de Beek D, Brouwer MC, Tunkel AR. Acute meningitis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 87.

  • Meninges of the brain

    Meninges of the brain - illustration

    The organs of the central nervous system (brain and spinal cord) are covered by connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.

    Meninges of the brain

    illustration

  • Meninges of the spine

    Meninges of the spine - illustration

    The organs of the central nervous system (brain and spinal cord) are covered by 3 connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.

    Meninges of the spine

    illustration

  • Central nervous system and peripheral nervous system

    Central nervous system and peripheral nervous system - illustration

    The central nervous system comprises the brain and spinal cord. The peripheral nervous system includes nerves outside the brain and spinal cord.

    Central nervous system and peripheral nervous system

    illustration

  • CSF cell count

    CSF cell count - illustration

    CSF (cerebrospinal fluid) is a clear fluid that circulates in the space surrounding the spinal cord and brain. A CSF cell count is a test to measure the number of red and white blood cells that are in CSF.

    CSF cell count

    illustration

  • Gram stain

    Gram stain - illustration

    A Gram stain is a test used to help identify bacteria. The tested sample can be taken from body fluids that do not normally contain bacteria, such as blood, urine, or cerebrospinal fluid. A sample can also be taken from the site of a suspected infection, such as the throat, lungs, genitals, or skin. Bacteria are classified as either Gram-positive or Gram-negative, based on how they color in reaction with the Gram stain. The Gram stain is colored purple. When combined with the bacteria in a sample, the stain will either stay purple inside the bacteria (Gram-positive), or it will turn pink (Gram-negative). Examples of Gram-positive bacteria include Streptococcus and Staphylococcus aureus, as well as bacteria that cause anthrax, diphtheria, and toxic shock syndrome. Examples of Gram-negative bacteria include Escherichia coli (E coli), Salmonella, Hemophilus influenzae, as well as many bacteria that cause urinary tract infections, pneumonia, or peritonitis. Gram stain can be done within a few hours. The results help providers choose the first antibiotics to use. Cultures of bacteria help identify specific bacteria, but take days to complete.

    Gram stain

    illustration

  • Meninges of the brain

    Meninges of the brain - illustration

    The organs of the central nervous system (brain and spinal cord) are covered by connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.

    Meninges of the brain

    illustration

  • Meninges of the spine

    Meninges of the spine - illustration

    The organs of the central nervous system (brain and spinal cord) are covered by 3 connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.

    Meninges of the spine

    illustration

  • Central nervous system and peripheral nervous system

    Central nervous system and peripheral nervous system - illustration

    The central nervous system comprises the brain and spinal cord. The peripheral nervous system includes nerves outside the brain and spinal cord.

    Central nervous system and peripheral nervous system

    illustration

  • CSF cell count

    CSF cell count - illustration

    CSF (cerebrospinal fluid) is a clear fluid that circulates in the space surrounding the spinal cord and brain. A CSF cell count is a test to measure the number of red and white blood cells that are in CSF.

    CSF cell count

    illustration

  • Gram stain

    Gram stain - illustration

    A Gram stain is a test used to help identify bacteria. The tested sample can be taken from body fluids that do not normally contain bacteria, such as blood, urine, or cerebrospinal fluid. A sample can also be taken from the site of a suspected infection, such as the throat, lungs, genitals, or skin. Bacteria are classified as either Gram-positive or Gram-negative, based on how they color in reaction with the Gram stain. The Gram stain is colored purple. When combined with the bacteria in a sample, the stain will either stay purple inside the bacteria (Gram-positive), or it will turn pink (Gram-negative). Examples of Gram-positive bacteria include Streptococcus and Staphylococcus aureus, as well as bacteria that cause anthrax, diphtheria, and toxic shock syndrome. Examples of Gram-negative bacteria include Escherichia coli (E coli), Salmonella, Hemophilus influenzae, as well as many bacteria that cause urinary tract infections, pneumonia, or peritonitis. Gram stain can be done within a few hours. The results help providers choose the first antibiotics to use. Cultures of bacteria help identify specific bacteria, but take days to complete.

    Gram stain

    illustration

 

Review Date: 9/10/2022

Reviewed By: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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