Population-Based Incidence and Characteristics of Adult Escherichia coli Bloodstream Infection in Queensland, Australia, From 2000 to 2019

Background There is increasing morbidity and mortality attributed to escalating incidence of Escherichia coli bloodstream infection (BSI). The epidemiology of E. coli BSI is dynamic and differs across populations. This study aimed to describe this epidemiology in Queensland, Australia. Methods Incident E. coli BSIs (new or recurring & GE;30 days from previous BSI) in adult (& GE;15 years) Queenslanders were identified from 2000 to 2019 using Queensland Health databases. Incidence rates, crude and standardized by age and gender, were calculated. Negative binomial regressions were performed to determine predictors of E. coli BSI incidence. Results From 2000 to 2019, 30 350 E. coli BSIs in 27 793 patients were detected; the standardized incidence rate almost doubled from 34.1 to 65.9 cases per 100 000 residents. Predictors of higher incidence rate were older age (& GE;65 years), comorbidity, and community-onset infection. Despite holding these factors constant, the incidence rate was estimated to increase 4% (adjusted incidence rate ratio [IRR], 1.04; 95% CI, 1.03-1.04) annually over the study period. Approximately 4.2% of E. coli isolates produced extended-spectrum beta-lactamase (ESBL-Ec), with most (95%) detected after 2010. The incidence rate of ESBL-Ec increased 25% (IRR, 1.25%; 95% CI, 1.2-1.3) annually, significantly faster than that of non-producers. Amikacin and carbapenems remain effective in vitro against ESBL-Ec BSI in Queensland. Conclusions The rise in E. coli BSIs is driven both by a higher infection rate and shifting epidemiology toward community-onset infections. These are likely attributed to an aging Australian population with increasing chronic comorbidity. The rapid expansion of ESBL-Ec in recent years is concerning and should be acknowledged for its implication in the community. This population-based study described significantly escalating incidence of both ESBL- and non-ESBL-producing E. coli bloodstream infections over a twenty-year period and identified predictors of higher incidence as community-onset infections, older age and comorbidity. Carbapenems remain effective in vitro to ESBL-producers.