Introduction: Carbapenem-resistant Enterobacteriaceae (CRE) infections, with limited treatment options, pose a significant public health challenge. In 2011, the CDC’s phenotypic CRE case definition was nonsusceptibility to ≥ 1 carbapenem and resistance to 3^rd generation cephalosporins but changed January 2016 to resistance to any carbapenem (including ertapenem). This study seeks to determine if this change influenced significant differences in patient characteristics.

Methods: CRE cases in Metro Atlanta, Georgia were collected from 2011-2016. Cumulative incidence per 100,000, odds ratios, and ꭓ²estimates were calculated to identify trends. A univariable analysis was conducted to examine risk factors. Adjusting for covariates, the final multivariable model included invasive infection as the outcome and the new definition as the predictor.

Results: A total of 1,144 CRE cases were confirmed from 2011-2016 in Metro Altanta. CRE incidence rates for all culture sources decreased pre-and post-definition change from 9.4 to 1.6. Central venous catheters and ICU stay 7 days prior, had the strongest association with invasive CRE infections; pre-(OR 5.9, 95% CI 1.4-4.3) and post-(OR 11.2, 95% CI 4.9-25.6) definition change. In the final model, the new definition (OR 0.6, 95% CI 0.4-0.9) predicted invasive infection.

Discussion: CRE cases, following the new CRE case definition, had a 40% lower odds of invasive infections than that of the former. The cause of this shift is unclear as more data on antibiotic resistance profiles is needed to assess the definition’s overall performance. However, the impact of the new definition on invasive CRE infections is measurable and warrants further analysis.