Gram-negative Bacterial Infection


Gram-negative bacteria are bacteria with strong walls. They can cause infections throughout the body. The infections can be serious and tough to treat.

Some gram-negative bacteria can cause certain types of :

  • 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

pneumonia lung fluid
Copyright © Nucleus Medical Media, Inc.


Bacteria are normally found in the body. 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 that pass into the body, 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 your symptoms and health history. A physical exam will be done.

An infection may be suspected by the symptoms.

A sample of fluids may be taken from the suspected area. The sample will be tested for bacteria. Samples may be taken 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

These tests are not always done. They may only be done for severe infections and those that do not get better.


The goal is to clear the infection. If not treated, gram negative bacteria can lead to serious problems and death.

Bacterial infections are treated with antibiotics. However, common antibiotics may not work for this type of infection. Older antibiotics may work better. The doctor may need to try different ones.


The risk of infection may be reduced by:

  • Good infection control in health care settings
  • Washing hands often
  • Not touching wounds or incisions—and keeping them clean and bandaged


Centers for Disease Control and Prevention
IDSA—Infectious Diseases Society of America


Infection Prevention and Control Canada
Public Health Agency of Canada


Antibiotic resistance threats in the United States, 2013. Centers for Disease Control and Prevention website. Available at: Accessed April 2, 2021.
Bacteremia with gram-negative bacilli. EBSCO DynaMed website. Available at: Accessed April 2, 2021.
Bacterial meningitis in adults. EBSCO DynaMed website. Available at: . Accessed April 2, 2021.
Carbapenem-resistant Enterobacteriaceae (CRE). EBSCO DynaMed website. Available at: . Accessed April 2, 2021.
Extended spectrum beta-lactamases (ESBLs). EBSCO DynaMed website. Available at: . Accessed April 2, 2021.
Gram-negative bacteria. National Institute of Allergy and Infectious Diseases website. Available at: Accessed April 2, 2021.
Gram-negative bacteria infections in healthcare settings. Centers for Disease Control and Prevention website. Available at: Accessed April 2, 2021.
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.
Last reviewed December 2020 by EBSCO Medical Review Board David L. Horn, MD, FACP
Last Updated: 4/2/2021

EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.

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.

To send comments or feedback to our Editorial Team regarding the content please email us at Our Health Library Support team will respond to your email request within 2 business days.