The Spatiotemporal Occurrence and Recovery of Shiga Toxin-producing Escherichia coli (STEC) in Well-sourced Drinking Water from Southern Alberta, Canada

• Author / Creator

  Reynolds, Colin

• Shiga toxin-producing Escherichia coli (STEC) are important enteric pathogens that cause significant morbidity and mortality worldwide, as well as in Canada. Drinking water is a key exposure pathway for STEC infection and the occurrence of these pathogens in drinking water sources represents an important knowledge gap in the epidemiological understanding of STEC-associated illness, particularly with regards to non-O157 STEC serogroups as well as unregulated well- sourced drinking water systems. The purpose of this study was to investigate the frequency and spatiotemporal patterns of STEC occurrence in non-municipal well- sourced drinking water in the southern region of the province of Alberta, Canada. Using Shiga toxin gene quantitative polymerase chain reaction analysis (stx qPCR) as a proxy, STEC were found in 8.0% of E. coli positive drinking water samples and 0.2% of all drinking water samples from across southern Alberta submitted to the Alberta Provincial Laboratory for Public Health (ProvLab) between 2004-2016. A statistically significant seasonal pattern of STEC occurrence that peaked in the summer months was detected, which coincides with well-established seasonal increases of reported STEC cases in both Alberta and Canada. Significantly greater annual STEC occurrence corresponded with years where extreme precipitation events occurred across this region and a STEC contamination event in an area of southern Alberta was detected in the early summer of 2005 using Kulldorff scan statistics. Twenty-one distinct STEC serotypes, including 6 of the 7 most clinically relevant serotypes in Alberta, were recovered from stx positive drinking water samples using a STEC-specific chromogenic growth media. Taken together, these findings demonstrate that STEC was consistently found in non-municipal well- sourced drinking water across southern Alberta and represents a public health risk to Canadians that rely on groundwater wells for their drinking water supplies. Furthermore, the seasonal alignment of increased STEC occurrence in non- municipal drinking water sources with patterns of increased STEC-associated illness highlights both the possibility of contaminated well water contributing to the seasonality of STEC infections in Canada, as well as the potential contribution of this exposure pathway to the overall burden of enteric disease.

• Subjects / Keywords

  • Non-O157
  • Shiga Toxin-producing Escherichia coli
  • Waterborne pathogens
  • Surveillance Epidemiology
  • Alberta
  • Spatial Epidemiology
  • E. coli
  • Environmental microbiology
  • Well water
  • CHROMagar STEC
  • VTEC
  • Kulldorff spatial scan statistic
  • Shiga toxin
  • Waterborne disease
  • GIS
  • Drinking water
  • Environmental health sciences
  • Enteric pathogens
  • STEC
  • O157
  • Seasonality
  • Public health

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3XG9FS9H

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.