ABSTRACT
Background and objective: Extended-spectrum β-lactamase (ESBL)-producing organisms have been reported among nosocomial pathogens. The objective of this study is to determine the risk factors for nosocomial infections in adults caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E-coli) or Klebsiella pneumoniae (K. pneumoniae) in regional and provincial government hospitals in Thailand.Methods: A nested case-control study was conducted, and the patients were enrolled between July 1 and December 31, 2007. We compared 288 patients with nosocomial infections caused by ESBL-producing E. coli or K. pneumoniae to 288 hospital-matched controls with nosocomial infections caused by non ESBL-producing E. coli or K. pneumoniae.Results: The independent risk factors associated with nosocomial infections caused by ESBL producing strains included Charlson comorbidity index (Odds ratio=1.18, 95% confidence interval (CI) =1.06-1.31, p-value=0.001) and previous third generation cephalosporin use (OR=4.82, 95% CI=3.23-7.21, p-value \< 0.001).Conclusion: This is the first nested case-control study regarding the risk factors of nosocomial infections caused by ESBL-producing organisms. The Charlson comorbidity index and previous third-generation cephalosporin use were the contributing factors of nosocomial infections caused by these organisms. An emphasis on appropriate use of the third-generation cephalosporins as well as effective infection control measures in patients with high comorbidity index are needed to reduce the incidence of nosocomial infections caused by these organisms.