Abstract and Introduction
Abstract
Objective. Describe the epidemiology of carbapenem-resistant Enterobacteriaceae (CRE) and examine the effect of lower carbapenem breakpoints on CRE detection.
Design. Retrospective cohort.
Setting. Inpatient care at community hospitals.
Patients. All patients with CRE-positive cultures were included.
Methods. CRE isolated from 25 community hospitals were prospectively entered into a centralized database from January 2008 through December 2012. Microbiology laboratory practices were assessed using questionnaires.
Results. A total of 305 CRE isolates were detected at 16 hospitals (64%). Patients with CRE had symptomatic infection in 180 cases (59%) and asymptomatic colonization in the remainder (125 cases; 41%). Klebsiella pneumoniae (277 isolates; 91%) was the most prevalent species. The majority of cases were healthcare associated (288 cases; 94%). The rate of CRE detection increased more than fivefold from 2008 (0.26 cases per 100,000 patient-days) to 2012 (1.4 cases per 100,000 patient-days; incidence rate ratio (IRR), 5.3 [95% confidence interval (CI), 1.22–22.7]; P = .01). Only 5 hospitals (20%) had adopted the 2010 Clinical and Laboratory Standards Institute (CLSI) carbapenem breakpoints. The 5 hospitals that adopted the lower carbapenem breakpoints were more likely to detect CRE after implementation of breakpoints than before (4.1 vs 0.5 cases per 100,000 patient-days; P < .001; IRR, 8.1 [95% CI, 2.7–24.6]). Hospitals that implemented the lower carbapenem breakpoints were more likely to detect CRE than were hospitals that did not (3.3 vs 1.1 cases per 100,000 patient-days; P = .01).
Conclusions. The rate of CRE detection increased fivefold in community hospitals in the southeastern United States from 2008 to 2012. Despite this, our estimates are likely underestimates of the true rate of CRE detection, given the low adoption of the carbapenem breakpoints recommended in the 2010 CLSI guidelines.
Introduction
Carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a global threat. Patients with CRE infections have adverse outcomes, including mortality risk ranging from 48%–71%. Multidrug-resistant organisms, such as CRE, have been labeled as "a serious threat to public health" by the Centers for Disease Control and Prevention (CDC) and "one of the three greatest threats to human health," by the World Health Organization. Although CRE are still relatively uncommon in the United States, the rate of carbapenem resistance among Enterobacteriaceae is increasing. Among cases due to Klebsiella pneumoniae, for example, the percentage due to meropenem-resistant strains increased from 0.6% to 5.4% from 2004 to 2008.
Little is known about the epidemiology of CRE in community hospitals, despite the fact that the majority of healthcare in the United States is provided in this setting. These hospitals often have difficulty identifying trends, given the sporadic occurrence of cases, and as a result are less likely to view CRE as an important pathogen in their facilities.
Despite the global emergence of CRE, no clear consensus has emerged in regard to the method of detection. Because of early studies that showed that some CRE had carbapenem minimum inhibitory concentrations (MICs) in the susceptible range, the Clinical and Laboratory Standards Institute (CLSI) recently lowered breakpoints for carbapenem antibiotics. Adherence to the new CLSI breakpoints requires that laboratories take additional steps to validate the lower breakpoints. Many laboratories have not yet adopted the new carbapenem breakpoints, potentially resulting in decreased detection and underestimation of CRE prevalence. The objectives of our study were to (1) describe the epidemiology of CRE in a network of community hospitals in the southeastern United States, (2) evaluate the methods that these hospitals use to detect CRE, and (3) better understand how differences in laboratory methods influence CRE detection.