Clinical epidemiology of carbapenem- resistant enterobacteriaceae in community hospitals: A case-case-control study

Background: The occurrence of carbapenem-resistant Enterobacteriaceae (CRE) has been increasing at an alarming rate worldwide. Despite that increase, there are limited data identifying risk factors. Objective: To evaluate risk factors associated with the acquisition of CRE among hospitalized patients. Methods: We performed a retrospective case-casecontrol study in 4 community hospitals from June 2007 through June 2012. Case group 1 (CG1) consisted of patients with CRE. Case group 2 (CG2) consisted of patients with carbapenem susceptible Enterobacteriaceae (CSE). CG2 patients were matched to CG1 patients by site of infection and species of Enterobacteriaceae. Hospitalized controls were matched 2:1 by date of admission and hospital location to patients in CG1. Two sets of analyses were conducted comparing demographics, comorbidities, and antibiotic exposures of CG1 and CG2 to controls and then contrasted to identify unique risk factors associated with CRE. Results: Overall, 104 patients (CG1, 25 patients; CG2, 29 patients, control, 50 patients) were evaluated. CRE and CSE consisted mostly of Klebsiella spp. (63%) from a urinary source (28%). In multivariable analyses, intensive care unit (ICU) stay (OR 12.48; 95% CI 1.14-136.62; p = 0.04) and cumulative number of antibiotic days (OR 1.47; 95% CI 1.02-2.16; p = 0.04) were distinct independent predictors of CRE isolation; whereas, cumulative health care exposures (OR 2.03; 95% CI 1.20-3.41; p < 0.01) and vancomycin exposure (OR 6.70; 95% CI 1.15- 38.91; p = 0.03) were predictors for CSE. Conclusions: CRE should be considered in patients requiring ICU admission, particularly those who have received multiple antibiotics. Antibiotic stewardship efforts should be directed at reducing all antibiotic exposures as opposed to any specific antibiotic class to reduce the risk of CRE.