Risk Factor and Outcome Evaluation in Patients with Carbapenem Resistant Enterobacteriaceae (CRE) in a Mid-Western Tertiary Care Academic Medical Center

Background: Increased use of carbapenems and emergence of novel β-lactamases have contributed to an increased prevalence of carbapenem-resistant Enterobacteriaceae (CRE). Identification of factors associated with CRE is important for both understanding the determinants of the acquisition, dissemination and outcomes of infections with these organisms. To our knowledge, CRE mortality has been previously compared to carbapenem-susceptible Enterobacteriaceae(CSE) and to uninfected controls but not to infected controls in general.

Methods:

We performed a retrospective cohort study to assess the risks for CRE isolation and mortality in three groups of hospitalized adults from January 2010 to March 2014: (i) patients from whom CRE was isolated, (ii) controls from whom CSE were isolated, and (iii) controls matched for the positive cultures at the same site as CRE patients. (iii) was inclusive of (ii). The demographics, comorbidities, and exposures of CRE cases were compared with the two control groups. Significant covariates were incorporated into multivariable models. In the mortality study, we evaluated the effect of CRE on 30-day mortality.

Results:

There were 53 patients with CRE isolation (8 died in 30 days [17%]), 26 patients with CSE isolation (0 died [0%]), and 54 controls (4 died [7.4%]). Independent risk factors for CRE isolation were Immunosuppression/Transplantation with (odds ratio [OR], 7.0; 95% confidence interval [CI], 1.1 to 43.3; P=0.04), hospitalization>2d within 90 days prior to this hospital admission stay (OR, 11.5; 95% CI, 1.8 to 72.6; P=0.01) and higher days of mechanical ventilation (OR, 2.2; 95% CI, 1.1 to 4.2; P=0.02). CRE was associated with death when patients with CRE were compared with control group 1 (CSE group) (P = 0.04) but not when compared with control group 2 (general infection group) (P=0.09). A logistic regression model (n=59) examining the factors for 30-day mortality found that only longer duration of mechanical ventilation was significantly associated with 30-day mortality (P=0.03) when compared to CSE control group.

Conclusion:

We have shown that patients with immunosuppression and/or transplantation status and prior hospitalization are at risk for CRE infection. Longer duration of mechanical ventilation is an independent predictor of 30-day mortality when compared to CSE but not when compared to infections in general.