Carbapenemase Production and Mortality Risk Among Carbapenem-Resistant Enterobacteriaceae Cases in Tennessee, United States

Abstract

Background: Carbapenem-resistant Enterobacteriaceae (CRE) are an urgent public health threat associated with poor patient outcomes. CRE that produce carbapenemase (CP-CRE) are of particular concern because the mechanism-conferring genes in plasmids can be transferred to other bacteria. CRE are reportable in Tennessee (TN); isolate submission is required for CP production and resistance mechanism testing. We aimed to compare patient characteristics and outcomes between CP-CRE and non–CP-CRE patients to guide potential public health interventions. Methods: A retrospective cohort study to compare 30-day mortality, and clinical characteristics of CP-CRE to non–CP-CRE patients was conducted. Laboratory data were gathered from CRE isolates of Tennessee residents from July 1, 2015, to June 30, 2018. The most recent Council of State and Territorial Epidemiologists CRE and CP-CRE case definition was used to confirm and classify cases. Healthcare exposures within 1 year prior to onset, demographic characteristics, and clinical characteristics were obtained by linking surveillance data with the inpatient and outpatient Tennessee hospital discharge data. Cases were also matched with Tennessee vital statistics data to determine all-cause 30-day mortality from the event date. We evaluated risk ratios of 30-day mortality with a multivariable regression model. Results: Among 1,034 CRE cases that had at least 1 isolate submitted to public health, 445 (43.0%) were CP-CRE and 589 (57.0%) were non–CP-CRE. Among CP-CRE isolates, the blaKPC gene was found in 434 (98.9%). CP-CRE cases were more likely to have isolates from normally sterile sites, to have an organism with elevated resistance to meropenem (minimum inhibitory concentration, >16 µg/mL), to have prior admission to a long-term acute-care hospital, and to live in a nursing home (all P < .001). Also, 77 CP-CRE cases (17.3%) and 56 non–CP-CRE cases (9.6%) died within 30 days of infection onset. The risk of 30-day mortality was 57% higher for CP-CRE (adjusted risk ratio, 1.57; 95% CI:, 1.10–2.23) compared to non–CP-CRE patients after adjusting for comorbidities, nursing home residence, and prior healthcare exposures. Conclusions: CP-CRE cases had poorer outcomes than non–CP-CRE cases. This may be related in part to a higher proportion of sterile site infections among CP-CRE cases; our study was underpowered to analyze this subpopulation of sterile site cases. We plan to continue monitoring and performing analyses as mortality and hospital discharge data from more recent years become available and as more cases accumulate.Funding: NoneDisclosures: None