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Gram-negative Bacterial Infection

  • Cynthia M. Johnson, MA
Publication Type:


Gram-negative Bacterial Infection


Gram-negative bacteria can cause infections throughout the body. The infections can be serious and hard to treat.

Some gram-negative bacteria can result in:

  • Food poisoning
  • Infections of the:
    • Stomach and intestines
    • Urinary tract
    • Lungs
    • Blood
  • Meningitis
  • Wound infections
  • Sexually transmitted infections, such as gonorrhea
Development of Pneumonia in the Air Sacs of the Lungs.

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Bacteria are normally found in the body. Gram-negative bacterial infections can happen if bacteria:

  • Increase in large amounts
  • Are aggressive
  • Are not kept in check by the immune system

Gram negative bacteria can pass to the body from:

  • Medical devices, such as IVs or catheters
  • Open wounds
  • Contact with someone who carries gram negative bacteria

Risk Factors

Gram negative bacterial infections are most common in hospitals. The risk increases with the length of the stay.

Other things that raise the risk are:


Symptoms depend on the site of the infection. Fever is a common sign.


The doctor will ask about symptoms and past health. A physical exam will be done.

Tests may be done to look for signs of the bacteria. This can be done with:

  • Blood tests and culture
  • Urine tests and culture
  • Sputum samples
  • Stool samples
  • Lumbar puncture—to test fluid around the brain and spinal cord
  • Cultures of abscesses, sores, soft tissues, wounds, or other areas


The goal is to clear the infection. If not treated, gram negative bacteria can lead to serious problems. It can even become deadly.

Bacterial infections are treated with antibiotics, but the ones that are most often used may not treat this type of infection. Older antibiotics may work better. If one antibiotic does not work, another may be tried until the infection goes away.


The risk of gram-negative bacterial infection may be lowered by:

  • Practicing proper handwashing
  • Not touching wounds or incisions—and keeping them clean and bandaged




  • Antimicrobial (drug) resistance. National Institute of Allergy and Infectious Diseases website. Available at: https://www.niaid.nih.gov/research/antimicrobial-resistance.
  • Bacteremia with gram-negative bacilli. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/bacteremia-with-gram-negative-bacilli.
  • Bacterial meningitis in adults. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/bacterial-meningitis-in-adults .
  • Carbapenem-resistant Enterobacteriaceae (CRE). EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/carbapenem-resistant-enterobacteriaceae-cre.
  • Extended spectrum beta-lactamases (ESBLs). EBSCO DynaMed website. Available at: https://www.dynamed.com/drug-review/extended-spectrum-beta-lactamases-esbls.
  • Gram-negative bacteria infections in healthcare settings. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/hai/organisms/gram-negative-bacteria.html.
  • MacVane SH. Antimicrobial resistance in the intensive care unit: a focus on gram-negative bacterial infections. J Intensive Care Med. 2017;32(1):25-37.


  • David L. Horn, MD, FACP
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.