Objective: The increasing prevalence of infections caused by extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella species (ESBL-EK) has become a growing concern in the hospitalized patient population. Previous studies on risk factors for infection with ESBL-EK have mainly focused on adult populations, and these findings may not be relevant among the pediatric population that experiences a unique set of health care exposures and underlying conditions. The objective of this study was to define the risk factors and outcomes associated with ESBL-EK bloodstream infections in children.
Methods: We conducted a nested case-control study using data from the Children's Hospital of Philadelphia from May 1, 1999, to September 30, 2003. Eligible patients were identified from the hospital database of microbiology laboratory records. All patients with ESBL-EK bloodstream infections were compared to a random sample of patients with non-ESBL-EK bloodstream infections. Risk factors analyzed included prior antimicrobial use, comorbid conditions, and demographic characteristics. Pulsed-field gel electrophoresis was performed to determine genetic relatedness of the ESBL-EK isolates.
Results: Thirty-five cases and 105 control subjects were included in the study. The median age among the cases was 2 years (interquartile range: 0-11), compared with 1 year (interquartile range: 0-8) among control subjects. Patients with ESBL-EK infections were 5.8 times (95% confidence interval: 1.9-17.7) more likely to have had exposure to an extended-spectrum cephalosporin in the 30 days before infection than those with non-ESBL-EK infections. Other independent predictors of ESBL-EK infection were being female, infection with a Klebsiella species, and steroid use in the 30 days before infection. All ESBL-EK isolates were susceptible to carbapenem antibiotics. Pulsed-field gel electrophoresis analysis revealed that the ESBL-EK isolates were polyclonal. Although a substantially higher proportion of children with ESBL-EK died (in-hospital mortality: 36% vs 13%), this difference was not statistically significant.
Conclusions: Receipt of extended-spectrum cephalosporins in the 30 days before infection by an Escherichia coli or Klebsiella species is significantly associated with having an ESBL-EK infection in hospitalized children. Curtailed use of cephalosporins among high-risk groups may reduce the occurrence of ESBL-EK infections. Future studies on identifying high-risk children and investigating the impact of curtailed third-generation cephalosporin use to limit additional emergence of ESBL-EK infections should be undertaken.