Epidemiology of Carbapenem-Resistant Enterobacteriaceae in 7 US Communities, 2012-2013

Abstract

Importance: Carbapenem-resistant Enterobacteriaceae (CRE) are increasingly reported worldwide as a cause of infections with high-mortality rates. Assessment of the US epidemiology of CRE is needed to inform national prevention efforts.

Objective: To determine the population-based CRE incidence and describe the characteristics and resistance mechanism associated with isolates from 7 US geographical areas.

Design, setting, and participants: Population- and laboratory-based active surveillance of CRE conducted among individuals living in 1 of 7 US metropolitan areas in Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, and Oregon. Cases of CRE were defined as carbapenem-nonsusceptible (excluding ertapenem) and extended-spectrum cephalosporin-resistant Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae complex, Klebsiella pneumoniae, or Klebsiella oxytoca that were recovered from sterile-site or urine cultures during 2012-2013. Case records were reviewed and molecular typing for common carbapenemases was performed.

Exposures: Demographics, comorbidities, health care exposures, and culture source and location.

Main outcomes and measures: Population-based CRE incidence, site-specific standardized incidence ratios (adjusted for age and race), and clinical and microbiological characteristics.

Results: Among 599 CRE cases in 481 individuals, 520 (86.8%; 95% CI, 84.1%-89.5%) were isolated from urine and 68 (11.4%; 95% CI, 8.8%-13.9%) from blood. The median age was 66 years (95% CI, 62.1-65.4 years) and 284 (59.0%; 95% CI, 54.6%-63.5%) were female. The overall annual CRE incidence rate per 100<000 population was 2.93 (95% CI, 2.65-3.23). The CRE standardized incidence ratio was significantly higher than predicted for the sites in Georgia (1.65 [95% CI, 1.20-2.25]; P < .001), Maryland (1.44 [95% CI, 1.06-1.96]; P = .001), and New York (1.42 [95% CI, 1.05-1.92]; P = .048), and significantly lower than predicted for the sites in Colorado (0.53 [95% CI, 0.39-0.71]; P < .001), New Mexico (0.41 [95% CI, 0.30-0.55]; P = .01), and Oregon (0.28 [95% CI, 0.21-0.38]; P < .001). Most cases occurred in individuals with prior hospitalizations (399/531 [75.1%; 95% CI, 71.4%-78.8%]) or indwelling devices (382/525 [72.8%; 95% CI, 68.9%-76.6%]); 180 of 322 (55.9%; 95% CI, 50.0%-60.8%) admitted cases resulted in a discharge to a long-term care setting. Death occurred in 51 (9.0%; 95% CI, 6.6%-11.4%) cases, including in 25 of 91 cases (27.5%; 95% CI, 18.1%-36.8%) with CRE isolated from normally sterile sites. Of 188 isolates tested, 90 (47.9%; 95% CI, 40.6%-55.1%) produced a carbapenemase.

Conclusions and relevance: In this population- and laboratory-based active surveillance system in 7 states, the incidence of CRE was 2.93 per 100<000 population. Most CRE cases were isolated from a urine source, and were associated with high prevalence of prior hospitalizations or indwelling devices, and discharge to long-term care settings.