Risks Factors for Infections with Extended-Spectrum Beta-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae at a Tertiary Care University Hospital in Switzerland

Background: There are considerable geographical differences in the occurrence of extended-spectrum beta-Lactamase (ESBL)-producing bacteria, both in the community and in the hospital setting. Our aim was to assess risk factors for bloodstream, urinary tract, and vascular catheter-associated infections with ESBL-producing Escherichia coli and Klebsiella pneumoniae at a tertiary care hospital in a low-prevalence country. Methods: We performed a case-control study comparing 58 patients with infections due to ESBL-producing E. coli or K. pneumoniae vs 116 controls with infections due to non-ESBL producing organisms at the University Hospital Zurich, Switzerland, between 1 July 2005 and 30 June 2007. Results: Cases included 15 outpatients and 43 inpatients. Multivariable analyses found three risk factors for ESBL-producing isolates: begin of symptoms or recent antibiotic pre-treatment in a foreign country (odds ratio [OR] 27.01, 95% confidence interval [CI] 2.38-1,733.28], p = 0.042), antibiotic therapy within the year preceding the isolation of the ESBL-producing strain (OR 2.88, 95% CI 1.13-8.49, p = 0.025), and mechanical ventilation (OR 10.56, 95% CI 1.06-579.10, p = 0.042). Conclusions: The major risk factors for infections due to ESBL-producing bacteria were travel in high-prevalence countries, prior antibiotic use, and mechanical ventilation during a stay in the intensive care unit. Community-acquired infections were documented in 17% of the patients. An early identification of risk factors is crucial to providing the patients an optimal empiric antibiotic therapy and to keep the use of carbapenems to a minimum.