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Klebsiella , Enterobacter , and Serratia Infections

By Larry M. Bush, MD, Affiliate Professor of Clinical Biomedical Sciences, Charles E. Schmidt College of Medicine, Florida Atlantic University; Affiliate Associate Professor of Medicine, University of Miami-Miller School of Medicine

Klebsiella, Enterobacter, and Serratia are closely related gram-negative bacteria that occasionally infect people in hospitals or in long-term care facilities.

  • These bacteria may infect the urinary or respiratory tract, intravenous catheters used to give drugs or fluids, burns, wounds made during surgery, or the bloodstream.

  • Identifying the bacteria in a sample taken from blood or from infected tissue confirms the diagnosis.

  • If the infection is acquired in the community, antibiotics can cure it, but if it is acquired in a health care facility, it is difficult to treat because bacteria tend to be resistant.

Klebsiella, Enterobacter, and Serratia bacteria reside in the intestine of many healthy people and rarely cause infection in them. Infections with these bacteria are often acquired in hospitals and long-term care facilities. They usually occur in people whose resistance to infection is weakened and/or who have a medical device (such as catheters, drains, and airway tubes) in their body.

These bacteria may infect different areas:

  • Urinary or respiratory tract (causing pneumonia, bladder infections, or kidney infections)

  • Catheters inserted into a vein (intravenous catheter), used to administer drugs or fluids

  • Burns

  • Wounds made during surgery

  • Bloodstream (causing bacteremia or sepsis)

Rarely, Klebsiella bacteria cause pneumonia in people who live outside a health care facility (in the community), usually in alcoholics, older people, people with diabetes, or people with a weakened immune system. Typically, this severe infection causes cough, bringing up a sticky, dark brown or dark red sputum, and collections of pus (abscesses) in the lung or in the membrane between the lungs and chest wall (empyema).

One species of Klebsiella can cause inflammation of the colon (colitis) after antibiotics are taken. This disorder is called antibiotic-associated colitis. The antibiotics kill bacteria that normally reside in the intestine. Then Klebsiella bacteria are able to multiply and cause problems. However, antibiotic-associated colitis usually results from toxins produced by Clostridium difficile (see Clostridium difficile -Induced Colitis).


  • Examination and culture of a sample of infected tissue

Doctors suspect one of these infections in people at high risk of getting one, such as people who live in a long-term care facility or in a place when there was an outbreak.

To confirm the diagnosis, doctors take a sample of sputum, lung secretions (obtained through a bronchoscope), blood, urine, or infected tissue. The sample is stained with Gram stain, cultured, and examined under a microscope. These bacteria can be readily identified.

Other tests depend on the type of infection. They may include imaging tests, such as ultrasonography, x-rays, and computed tomography (CT).

Bacteria identified in samples are tested to determine which antibiotics are likely to be effective (a process called susceptibility testing).


  • Antibiotics given intravenously

If Klebsiella pneumonia is acquired in the community, antibiotics, usually a cephalosporin (such as ceftriaxone) or fluoroquinolone (such as levofloxacin), given intravenously, can cure it.

If an infection with any of these three bacteria is acquired in a health care facility, the infection is difficult to treat because bacteria acquired in such facilities are usually resistant to many antibiotics.

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