Mortality risk of ESBL producers in Escherichia coli bacteraemia: a comprehensive analysis using the PROBAC cohort.

OBJECTIVE

The incidence of bloodstream infection (BSIs) due to extended-spectrum β-lactamase (ESBL) producing Escherichia coli is increasing worldwide. There is controversy as to whether ESBL production in itself is associated with higher mortality. The aim of this study is to evaluate the impact of ESBL production on mortality in BSIs due to E. coli considering the effect of confounders.

METHODS

PROBAC study is a prospective, multicentre, cohort study performed in 26 Spanish hospitals (October 2016-March 2017). All patients with E. coli BSIs were included. The outcome variable was all-cause 30-day mortality. Confounding was controlled by calculating a propensity score (PS) for ESBL production using baseline variables. PS were used as covariable, for matching, for inverse probability of treatment weight analysis and for stratified analysis within the PS quartiles.

RESULTS

A total of 2394 cases were included, of which 322 (13.5%) were ESBL-producing isolates. The frequency of appropriate empirical treatment, in ESBL-producing and non-ESBL-producing isolates, was 53.7% and 92.0%, respectively. Thirty-day mortality was 14.6% in ESBL-producing isolates versus 9.6% in non-ESBL-producing isolates (P = 0.006), for a crude OR of 1.61 (95% CI: 1.14-2.27; P = 0.006). When we adjusted by PS and appropriate empirical treatment, the OR changed to 1.12 (95% CI: 0.75-1.67; P = 0.584). Other PS applications provided similar results.

CONCLUSION

BSIs due to ESBL-producing E. coli were associated with higher mortality in the crude analyses; however, the estimate of the association is reduced after adjustment for baseline variables and empirical therapy, and is not significant in matched analysis.