Clinicians: Information about CRE

Clinicians play a critical role in helping to identify patients colonized or infected with CRE and preventing its spread.

What are CRE?

CRE stands for carbapenem-resistant Enterobacterales. Enterobacterales are an order of bacteria commonly found in people’s gastrointestinal tract that can cause infections both in healthcare and community settings.

All CRE are likely multidrug-resistant organisms and interventions might be required in healthcare settings to prevent transmission. However, a subset of CRE, called carbapenemase-producing CRE (CP-CRE), are currently believed to be primarily responsible for the increasing spread of CRE in the United States and have therefore been targeted for aggressive prevention.

What is the CDC CRE definition?

Enterobacterales that test resistant to at least one of the carbapenem antibiotics or produce a carbapenemase (an enzyme that can make them resistant to carbapenem antibiotics) are called CRE. Some Enterobacterales (e.g., Proteus spp., Morganella spp., Providencia spp.) have intrinsic elevated minimum inhibitory concentrations (MICs) to imipenem and therefore results for meropenem, doripenem, and ertapenem should be used for these organisms to determine if they meet the CRE definition.

In the United States, CRE are generally associated with healthcare settings, and approximately 30% of CRE carry a carbapenemase. These carbapenemase genes are often on mobile genetic elements, which can be easily shared between bacteria, leading to the rapid spread of resistance.

Why are CP-CRE considered epidemiologically important?

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Antibiotic Resistance Threats in the United States, 2019

  • CRE organisms are often resistant to multiple classes of antibiotics, substantially limiting treatment options.
  • Infections caused by these organisms are associated with high mortality rates among hospitalized patients, up to 50% in some studies.
  • Many CRE produce carbapenemases, which can be transmitted from Enterobacterales to other germs, facilitating spread of resistance.
  • Enterobacterales are a common cause of infections in both community and healthcare settings. Although CRE is currently primarily associated with inpatient healthcare settings, it has the potential to spread to community settings.

For these reasons, CDC has developed resources to support healthcare providers as they screen patients for CRE and take action to decrease transmission of CRE.

What is the difference between CRE colonization and infection?

When found in clinical culture, CRE can represent an infection or colonization. Colonization means that the organism can be found in or on the body but it is not causing any symptoms or disease. Colonizing CRE strains can go on to cause infections or spread to other patients. Colonization screening is a CDC-recommended intervention that can help stop the spread of CRE. The AR Lab Network offers free colonization screening.

Which patients are at increased risk for CRE acquisition?

The main risk factors for CRE acquisition in the United States include exposure to healthcare and exposure to antibiotics. Healthcare-related risk factors include requiring help with most activities of daily living, like toileting and bathing, exposure to an intensive care unit, and mechanical ventilation. Several antibiotics have been associated with getting CRE, including carbapenems, cephalosporins, fluoroquinolones, and vancomycin.

How are CRE transmitted?

In healthcare settings, CRE are transmitted from person to person, often via the hands of healthcare personnel or through contaminated medical equipment. Additionally, sink drains and toilets are increasingly recognized as an environmental reservoir and CRE transmission source.

What infections do CRE cause?

CRE can cause infections in almost any body part, including bloodstream infections, ventilator-associated pneumonia, and intra-abdominal abscesses. Based on information from a CDC pilot surveillance system, most CRE infections involve the urinary tract, often in people who have a urinary catheter or have urinary retention.

What can clinicians do to prevent CRE transmission?

  • Know if patients with CRE are admitted to your facility and stay aware of CRE infection rates in your facility.
  • When you transfer a patient with CRE, use an inter-facility transfer form to alert the receiving facility during the transition of care.
  • Ask if a patient has received medical care somewhere else, including another facility or other countries.
  • Screen patients who have had an overnight stay in a healthcare facility outside the United States in the prior 6 months for the presence of carbapenemase-producing CRE. Free admission screening is available through the AR Lab Network. Contact your HAI coordinator for more information on accessing AR Lab Network testing.
  • Whenever possible, place patients currently or previously colonized or infected with CRE in a private room with a bathroom and dedicate noncritical equipment (e.g., stethoscope, blood pressure cuff) to CRE patients.

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  • Wear a gown and gloves when caring for patients with CRE.
  • Perform hand hygiene—use alcohol-based hand rub or wash hands with soap and water before and after contact with patient or their environment.
  • Make sure labs immediately alert clinical and infection prevention staff when CRE are identified. If your laboratory does not perform testing for carbapenemases, talk to your HAI coordinator about getting isolates tested through the AR Laboratory Network.
  • Prescribe and use antibiotics appropriately.
  • Discontinue devices like urinary catheters as soon as no longer necessary.
  • When a patient with an unusual type of carbapenemase-producing CRE is identified in your facility, work with public health to prevent spread, including following guidance to assess for ongoing transmission.

When can Contact Precautions be discontinued for patients colonized or infected with CRE?

There is currently not enough information for CDC to make a general recommendation on when isolation can be discontinued for patients colonized or infected with CRE. CRE colonization can be prolonged (> 6 months). Across multiple studies, predictors of prolonged CRE carriage have been found to include:

  • exposure to antibiotics
  • presence of an invasive device
  • higher Charlson’s co-morbidity scores
  • number of hospital admissions
  • admission from another facility
  • admission from or discharge to a long-term care facility [Schechner et al., 2011; Feldman et al., 2013; Zimmerman et al., 2013]

Presence of these predictors should be considered when deciding whether to discontinue Contact Precautions.

If considering discontinuing Contact Precautions based on the results of surveillance cultures, it is appropriate to wait for at least 3 to 6 months since last positive culture or screen.  The decision to discontinue Contact Precautions for an individual with a history of colonization or infection with CRE should be made in consultation with public health. In general, failure to identify CRE from at least two sets of screening cultures are the minimum criteria that should be met before an episode of colonization is considered resolved. Additionally, retesting of the site(s) that were positive initially from clinical cultures is usually indicated, particularly non-sterile sites such as a wound or urine.