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This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

CRE superbug continues to increase, with infections beyond the hospital, high mortality rates

Relatively uncommon in the United States before 2000, carbapenem-resistant Enterobacteriaceae (CRE) continue a dramatic increase in health care settings, moving across the health care continuum and causing infections that are difficult to treat and have high mortality, the Centers for Disease Control and Prevention reports.

Although CRE remain relatively uncommon in most acute-care hospitals in the United States, they have become an increasingly recognized cause of infection during the past decade, especially among Klebsiella, likely because of the emergence of carbapenemase-producing strains.

Enterobacteriaceae are a family of bacteria that commonly cause infections in health-care settings as well as in the community. Among Enterobacteriaceae, resistance to broad-spectrum carbapenem antimicrobials has been uncommon. Although the CRE family includes more than 70 genera, the health-care–associated Enterobacteriaceae most commonly reported to CDC's National Healthcare Safety Network (NHSN) surveillance system are Escherichia coli, Klebsiella species, and Enterobacter species.

The past several decades have seen the spread of with resistance to broad-spectrum antimicrobials; however, clinicians in the United States have relied on the carbapenem antimicrobial class (imipenem, meropenem, doripenem, and ertapenem) to treat infections caused by these resistant organisms. Unlike resistance in methicillin-resistant Staphylococcus aureus (MRSA), which is one bacterial species and is mediated by a single mechanism, carbapenem resistance is complex; it can occur in different Enterobacteriaceae and be mediated by several mechanisms, including production of enzymes that inactivate carbapenems (carbapenemases).

Klebsiella pneumoniae carbapenemase (KPC), an enzyme encoded by a highly transmissible gene, was first identified from a Klebsiella isolate in 2001 and has now spread widely throughout the United States and around the world. In addition to KPC, a number of additional carbapenemases that have emerged among Enterobacteriaceae outside the United States (e.g., New Delhi metallo-beta-lactamase [NDM]) have been identified in this country. CRE can spread in health-care settings and cause infections with mortality rates of 40% to 50%.

State and local health departments are well positioned to lead CRE control efforts because of their expertise in surveillance and prevention and their ability to interact among all the health-care facilities in their jurisdiction. To date, many health departments have conducted surveillance efforts in an attempt to identify the CRE incidence in their region. In addition, six states have made CRE reportable, and three additional states are actively pursuing this option. Requiring CRE reporting can allow for a better understanding of the changing CRE burden and can help facilitate intervention. Beyond surveillance, several states have developed and implemented plans to assist health-care facilities with control efforts when CRE are identified. As new MDROs emerge over time, this regional approach to MDRO prevention has implications beyond CRE as well.

The high proportion of CRE in non-hospital settings in 2012 highlights the need to expand prevention outside of short-stay acute-care hospitals into settings that, historically, have had less developed infection prevention programs. Additional research is needed to clarify unanswered questions, including assessing which CRE prevention strategies are most effective and investigating new prevention approaches such as decolonization. Fortunately, many regions are in a position to prevent the further emergence of these organisms if they act aggressively. To do so will require expanded and coordinated action from clinicians, facility administrators, and public health officials, the CDC urges.