About 3 in every 100,000 individuals developed a carbapenem-resistant Enterobacteriaceae infection in 2012-2013, most of whom had previously been hospitalized or had an indwelling device, researchers reported Oct. 5 in JAMA.
The relatively low incidence of these serious infections compared with other resistant organisms “highlights that CRE are emerging and suggests that control interventions implemented now could have a substantial effect,” wrote Dr. Alice Guh of the Centers for Disease Control and Prevention in Atlanta, and her associates. But the high rates of recent hospitalizations and discharges to nursing homes underscore the need for local control efforts, the researchers added.
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Carbapenem-resistant Enterobacteriaceae have become a global public health problem since emerging in 2001. In 2012, the Emerging Infections Program of the CDC began active CRE surveillance in metropolitan areas of Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, and Oregon. The researchers studied reported cases of carbapenem-nonsusceptible (excluding ertapenem) and extended-spectrum cephalosporin-resistant Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae complex, Klebsiella pneumoniae, and Klebsiella oxytoca infections cultured from urine or sterile sites (JAMA. 2015 Oct 5, doi:10.1001/jama.2015.12480.).
In all, 599 CRE infections occurred in 481 individuals, including 87% in urine and 11% in sterile sites, the investigators reported. Patients averaged 66 years of age and 59% were female. Overall CRE incidence was 2.93 cases per 100,000 population – substantially lower than rates of methicillin-resistant Staphylococcus aureus (about 25 per 100,000 population), invasive candidiasis (13-26 per 100,000 population), and Clostridium difficile (147 per 100,000 population).
Most of the CRE infections were among individuals who has been hospitalized in the past year (75%), who had an indwelling device (73%), or who had been discharged to a long-term care setting (56%). The indwelling devices with the highest rates of infection were urinary catheters, central venous catheters, and gastrostomy or jejunostomy tubes.
The case-fatality rate was 9% overall, but exceeded 27% when CRE was isolated from sterile sites, according to the study.
The standardized incidence ratio was significantly higher than predicted for sites in Georgia, Maryland, and New York, but significantly lower than expected for sites in Colorado, New Mexico, and Oregon. Such heterogeneity “further highlights the need to understand the local epidemiology to tailor prevention efforts in individual regions of the United States,” the researchers wrote.
And only 48% of CRE strains produced a carbapenemase, which carries antimicrobial resistance genes on mobile plasmids that can move between organisms, allowing for a potentially wider and more rapid spread. This suggests “the potential need for a tiered response to these organisms as well as the need for more rapid and readily available laboratory tests to differentiate these strains,” the researchers added.
The study was funded by the CDC Emerging Infections Program and the National Center for Emerging and Zoonotic Infectious Diseases. The researchers reported having no financial disclosures.