Klebsiella (CRE)

In 2017, CRE caused an estimated 13,100 infections in hospitalized patients, and 1,100 estimated deaths in the United States. Primarily CRE is associated with inpatient healthcare settings, with exposure to antibiotics an additional risk factor. Klebsiella was the first identified CRE organism, detected in the United States in 2001, and is currently the most common CRE in the US.


CRE or Carbapenem-resistant Enterobacteriaceae, are a group within the large bacterial family of Enterobacteriaceae that are resistant to a group of antibiotics called carbapenems or produce a carbapenemase (an enzyme that can make bacteria resistant to carbapenems). The most common CRE organism in the United States is Klebsiella pneumoniae. K. pneumoniae are Gram-negative rod-shaped bacteria, found in the intestines. There are several factors that mediate its infectivity including, adherence factors, capsule production, LPS, and siderophore activity. The Capsule is a viscous polysaccharide made up of repeating subunits, and is able to inhibit or impair killing of the bacteria by host cells. Siderophores are small compounds that bind iron really well, and act to transport iron across cell membranes. Iron is essential for K. pneumoniae to grow, but host cells also require iron, so the bacteria have to compete for the available iron which is frequently in limited supply, which is where the importance of siderophores comes into play.

Klebsiella Infection


CRE can cause infections in almost any body part, including infections in the bloodstream, pneumonia associated with a ventilator, and abscesses in the abdomen. Most CRE infections are in the urinary tract however, often in patients with a urinary catheter or have urinary retention. Infections are usually caused by contact with wounds or stool from infected people, via the hands of healthcare workers, or medical equipment and devices not correctly cleaned.

CRE Antibiotic Resistance

CRE are a major concern for patients in healthcare settings because they are resistant to carbapenem antibiotics, which are considered the last line of defense to treat multidrug-resistant bacterial infections. Often, high levels of antibiotic resistance in CRE leave only treatment options that are more toxic and less effective.