Klebsiella, Enterobacter, and Serratia are closely related gram-negative bacteria that occasionally infect people in hospitals or in long-term care facilities.
Klebsiella bacteria reside in the intestine of up to one third of healthy people. Enterobacter and Serratia bacteria usually reside outside the body, often in hospitals and long-term care facilities. People in such places can become infected.
These bacteria may infect different areas:
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, this type of colitis usually results from toxins produced by Clostridium difficile (see see Clostridium difficile-Induced Colitis).
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).
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.
Last full review/revision September 2008 by Matthew E. Levison, MD