Evaluation of risk factors for the acquisition of bloodstream infections with extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella species in the intensive care unit; antibiotic management and clinical outcome

Abstract

Controlled studies that address risk factors for, and clinical outcomes after, infection with extended-spectrum beta-lactamase (ESBL)-producing organisms are scant, particularly in the intensive care unit (ICU). Our objectives were to elucidate risk factors for the acquisition of ESBL-producing organisms in ICU; and to compare mortality in patients with ESBL- and non-ESBL bloodstream infections (BSIs) after controlling for disease severity and timeliness of appropriate antibiotic therapy. A retrospective cohort study was undertaken in the ICU from March 2004 to May 2006. Cases included all adult ICU patients with a BSI due to an ESBL-producing E. coli or Klebsiella spp. (N=16); controls (N=39) comprised ICU patients with a BSI caused by a non-ESBL-producing E. coli or Klebsiella spp. Disease severity was measured using APACHE (Acute Physiological Assessment and Chronic Health Evaluation) and SOFA (Sequential Organ Failure Assessment) scores. Outcomes were recorded as discharge or death due to all causes. Although no statistically significant associations were demonstrated between individual risk factors and the acquisition of an ESBL-producing organism, appropriate therapy was delayed in cases (OR: 9.17; 95% CI: 2.00-42.20; P=0.0005) and survival estimates demonstrated a significantly increased early (<25 days after infection) mortality (OR for death 3.93; 95% CI: 1.05-14.63; P=0.03). Mortality in ICU, when adjusted for disease severity and appropriate antimicrobial therapy, though significant needs to be treated with caution due to the small number of cases (N=16 in 2 years). We believe that a high index of suspicion, early appropriate therapy and strict adherence to infection control are indicated in all patients at risk in ICU.