FAQs about Choosing and Implementing a CRE Definition
Introduction
Carbapenem resistance among Enterobacteriaceae is complex; unlike methicillin resistance among Staphylococcus aureus which, for the most part, represents one resistance mechanism in one species of bacteria, Enterobacteriaceae include more than 70 different genera and many different mechanisms can lead to carbapenem resistance. All carbapenem-resistant Enterobacteriaceae (CRE), regardless of the mechanism underlying the carbapenem resistance, are likely multidrug-resistant organisms for which interventions might be required in healthcare settings to prevent transmission. However, 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. A reliable way to differentiate CP-CRE from non-CP-CRE might help guide such targeting by identifying the organisms of greatest epidemiologic interest. Because mechanism testing is not recommended for guiding therapeutic decisions, this testing is not routinely performed in many U.S. clinical laboratories, so phenotypic definitions, based on the bacteria’s antibiotic susceptibility pattern, are the primary way clinical laboratories and infection prevention teams attempt to identify CP-CRE; although no phenotypic definition will perform perfectly in distinguishing between CP-CRE and non-CP-CRE.
The previous CDC CRE definition (nonsusceptible to imipenem, meropenem, or doripenem, AND resistant to all third generation cephalosporins tested) was designed to be more specific for CP-CRE; however, it has proven to be complicated, difficult to implement, and has been found to miss some CP-CRE. In January 2015, The Centers for Disease Control and Prevention (CDC) modified its surveillance definition for CRE to the current definition (resistant to imipenem, meropenem, doripenem, or ertapenem OR documentation that the isolate possess a carbapenemase). The following document provides answers to frequently asked questions from healthcare facilities and laboratories about choosing and implementing a CRE definition.
- Page last reviewed: June 2, 2015
- Page last updated: June 29, 2015
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