Effect of varying federal definitions on prevalence and characteristics associated with carbapenem-resistant Enterobacteriaceae in veterans with spinal cord injury

Background: Patients with spinal cord injury (SCI) have a high risk for multidrug-resistant organisms, including carbapenem-resistant Enterobacteriaceae (CRE). Accurate and easily applied definitions are critical to identify CRE. This study describes CRE and associated characteristics in veterans with SCI per Centers for Disease Control and Prevention (CDC) and Department of Veterans Affairs (VA) definitions. Methods: A retrospective cohort of veterans with SCI and more than 1 culture with Escherichia coli, Klebsiella spp and/or Enterobacter spp between 2012 and 2013 was examined. Antibiotic susceptibility criteria of pre-2015 (CDC1) and post-2015 (CDC2) CDC definitions and pre-2017 (VA1) and post-2017 (VA2) VA definitions were used to identify CRE. CRE prevalence and characteristics are described for isolates meeting each definition, and agreement was assessed with the Cohen kappa. Results: We reviewed 21,514 isolates cultured from 6,974 veterans; 423 isolates met any CRE definition. Although agreement among definitions was high (kappa = 0.82-0.93), definitions including ertapenem resistance led to higher CRE prevalence (VA1 = 1.7% and CDC2 = 1.9% vs VA2 = 1.4% and CDC1 = 1.5%). Forty-four of 142 VA facilities had more than 1 CRE case defined by VA2; 10 facilities accounted for 60% of CRE cases. Almost all CRE was isolated from high-complexity, urban facilities, and the South had the highest proportion of CRE. Conclusions: Varying federal definitions give different CRE frequencies in a high-risk population. Definitions including ertapenem resistance resulted in higher CRE prevalence but may overemphasize noncarbapenemase isolates. Thus, both federal definitions now highlight the importance of carbapenemase testing.