Efficacy of Admission Screening for Extended-Spectrum Beta-Lactamase Producing Enterobacteriaceae

Objective: We hypothesized that admission screening for extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) reduces the incidence of hospital-acquired ESBL-E clinical isolates. Design: Retrospective cohort study. Setting: 12 hospitals (6 screening and 6 non-screening) in Toronto, Canada. Patients: All adult inpatients with an ESBL-E positive culture collected from 2005-2009. Methods: Cases were defined as hospital-onset (HO) or community-onset (CO) if cultures were positive after or before 72 hours. Efficacy of screening in reducing HO-ESBL-E incidence was assessed with a negative binomial model adjusting for study year and CO-ESBL-E incidence. The accuracy of the HO-ESBL-E definition was assessed by re-classifying HO-ESBL-E cases as confirmed nosocomial (negative admission screen), probable nosocomial (no admission screen) or not nosocomial (positive admission screen) using data from the screening hospitals. Results: There were 2,088 ESBL-E positive patients and incidence of ESBL-E rose from 0.11 to 0.42 per 1,000 inpatient days between 2005 and 2009. CO-ESBL-E incidence was similar at screening and non-screening hospitals but screening hospitals had a lower incidence of HO-ESBL-E in all years. In the negative binomial model, screening was associated with a 49.1% reduction in HO-ESBL-E (p<0.001). A similar reduction was seen in the incidence of HO-ESBL-E bacteremia. When HO-ESBL-E cases were re-classified based on their admission screen result, 46.5% were positive on admission, 32.5% were confirmed as nosocomial and 21.0% were probable nosocomial cases. Conclusions: Admission screening for ESBL-E is associated with a reduced incidence of HO-ESBL-E. Controlled, prospective studies of admission screening for ESBL-E should be a priority.