Detection, Characterization, and Typing of Shiga Toxin-Producing Escherichia coli.

Brendon D Parsons,Linda Chui,Byron M Berenger,Nathan Zelyas

doi:10.3389/fmicb.2016.00478

Abstract

Shiga toxin-producing Escherichia coli (STEC) are responsible for gastrointestinal diseases reported in numerous outbreaks around the world. Given the public health importance of STEC, effective detection, characterization and typing is critical to any medical laboratory system. While non-O157 serotypes account for the majority of STEC infections, frontline microbiology laboratories may only screen for STEC using O157-specific agar-based methods. As a result, non-O157 STEC infections are significantly under-reported. This review discusses recent advances on the detection, characterization and typing of STEC with emphasis on work performed at the Alberta Provincial Laboratory for Public Health (ProvLab). Candidates for the detection of all STEC serotypes include chromogenic agars, enzyme immunoassays (EIA) and quantitative real time polymerase chain reaction (qPCR). Culture methods allow further characterization of isolates, whereas qPCR provides the greatest sensitivity and specificity, followed by EIA. The virulence gene profiles using PCR arrays and stx gene subtypes can subsequently be determined. Different non-O157 serotypes exhibit markedly different virulence gene profiles and a greater prevalence of stx1 than stx2 subtypes compared to O157:H7 isolates. Finally, recent innovations in whole genome sequencing (WGS) have allowed it to emerge as a candidate for the characterization and typing of STEC in diagnostic surveillance isolates. Methods of whole genome analysis such as single nucleotide polymorphisms and k-mer analysis are concordant with epidemiological data and standard typing methods, such as pulsed-field gel electrophoresis and multiple-locus variable number tandem repeat analysis while offering additional strain differentiation. Together these findings highlight improved strategies for STEC detection using currently available systems and the development of novel approaches for future surveillance.

Highlights

Shiga toxin-producing Escherichia coli (STEC) encompass a heterogeneous group of enteric pathogens responsible for numerous sporadic infections and large outbreaks worldwide
This creates a gap in diagnostics; since 50% or more of STEC infections may be caused by non-O157 STEC, our surveillance and understanding of the epidemiology of STEC disease is incomplete (Fey et al, 2000; Jelacic et al, 2003; Thompson et al, 2005; Chui et al, 2011; Couturier et al, 2011; Scallan et al, 2011; Gould et al, 2013; STEC, National Surveillance Summary, 2014)
While the detection of Shiga toxins (Stx) is a direct way to determine if clinical specimens harbor STEC, there has been much interest in nucleic acid-based methods to detect the presence of the stx genes in stools

Summary

Introduction

Shiga toxin-producing Escherichia coli (STEC) encompass a heterogeneous group of enteric pathogens responsible for numerous sporadic infections and large outbreaks worldwide. Laboratories have become proficient at detecting O157:H7 infections, they often do not screen stools for other STEC serotypes. This creates a gap in diagnostics; since 50% or more of STEC infections may be caused by non-O157 STEC, our surveillance and understanding of the epidemiology of STEC disease is incomplete (Fey et al, 2000; Jelacic et al, 2003; Thompson et al, 2005; Chui et al, 2011; Couturier et al, 2011; Scallan et al, 2011; Gould et al, 2013; STEC, National Surveillance Summary, 2014)

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Conclusion