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Purpose: Despite the increasing rate of carbapenem-resistant Enterobacteriaceae (CRE), there are limited data identifying risk factors. This study evaluated risk factors associated with the acquisition of CRE among hospitalized patients.
Methods: We performed a retrospective matched case-case-control study in four community hospitals from June 2007 through November 2011. Case Group (CG) 1 comprised of patients with CRE. CG 2 comprised of patients with carbapenem-susceptible Enterobacteriaceae (CSE). CG 2 patients were matched to CG 1 patients by site of infection and specific species of Enterobacteriaceae. Hospitalized controls were matched 2:1 by date of admission and hospital location to patients in CG 1. Two sets of analyses were conducted comparing demographics, comorbidities and antibiotic exposures of CG 1 and CG 2 to controls then contrasted to identify unique risk factors associated with CRE.
Results: Overall, 104 patients (CG 1 – 25 patients; CG 2 – 29 patients, Control Group – 50 patients) were evaluated. CRE and CSE comprised mostly of Klebsiella species (64%) from a urinary source (28%). In univariate analysis, renal failure (p<0.001), exposure to fluroquinolones (p<0.01), carbapenems (p<0.001), aminoglycosides (p<0.01), poor functional status (p<0.01), ICU stay (p < 0.01), cumulative number of antibiotics exposures (p <0.001), and cumulative number of antimicrobial days by “time at risk” ratio (p<0.001) were significantly higher in CG 1 than controls. In multivariable analysis, poor functional status (OR 4.43, CI 2.25-8.73; p<.01), ICU stay (8.9, CI 3.49-23.03 p < 0.01), and cumulative number of antibiotics exposures (p <0.01) were distinct independent predictors of CRE isolation whereas cumulative healthcare exposures (p<0.01) and vancomycin exposure (OR 2.5, CI 1.63-3.84; p<0.01) were predictors for CSE.
Conclusion: CRE should be considered in patients with poor functional status requiring ICU admission, particularly those who have received multiple antibiotics.