Molecular epidemiology of Escherichia coli causing bloodstream infections in a centralized Canadian region: a population-based surveillance study

Abstract

Objectives: Escherichia coli is a leading cause of bloodstream infections worldwide, and is responsible for substantial patient morbidity, mortality and healthcare expenditure. Understanding the molecular epidemiology of E. coli will aid in designing superior treatment and prevention strategies.

Methods: We undertook a population-based surveillance study describing the clinical factors, susceptibility patterns, incidence rates and geographical distribution of sequence types (STs) among E. coli isolates (n = 686) causing incident bloodstream infections in a centralized Canadian region during 2016. STs were identified using a seven-single-nucleotide-polymorphism quantitative PCR (n = 422) and sequencing of certain house-keeping genes (n = 249).

Results: The annual population incidence rate of E. coli bloodstream infections was 48.8/100 000 patient years, and five dominant clones (ST131, ST73, ST69, ST95 and ST1193) accounting for 55% (378/686) of the population were identified, each with a specific geographical distribution within Calgary. ST131 was the most common (overall incidence rate of 10.4/100 000 patient years), an antimicrobial-resistant (AMR) clone affecting mainly the elderly and the very young. ST131 was common among residents in long-term care with an incidence rate of 312.5/100 000 patient years. ST73 was associated with community infections in the elderly, while ST69 and ST95 had increased incidence rates among females. ST1193 was the second most AMR clone and was associated with bloodstream infections in elderly males.

Conclusions: This study showed that E. coli clones have unique characteristics in a well-defined human population. The elimination of ST131 would substantially decrease the overall incidence rate and AMR burden among E. coli bloodstream infections in the Calgary region, leading to considerable public health benefits.

Keywords: Bloodstream infections; Escherichia coli; Molecular epidemiology; Population-based surveillance.