Phenotypic and Genotypic Characteristics of Shiga Toxin-Producing Escherichia coli Isolated from Surface Waters and Sediments in a Canadian Urban-Agricultural Landscape

Abstract

A hydrophobic grid membrane filtration—Shiga toxin immunoblot method was used to examine the prevalence of Shiga toxin-producing Escherichia coli (STEC) in four watersheds located in the Lower Mainland of British Columbia, Canada, a region characterized by rapid urbanization and intensive agricultural activity. STEC were recovered from 21.6, 23.2, 19.5, and 9.2% of surface water samples collected monthly from five sites in each watershed over a period of 1 year. Overall prevalence was subject to seasonal variation however, ranging between 13.3% during fall months and 34.3% during winter months. STEC were also recovered from 23.8% of sediment samples collected in one randomly selected site. One hundred distinct STEC isolates distributed among 29 definitive and 4 ambiguous or indeterminate serotypes were recovered from water and sediments, including isolates from Canadian “priority” serogroups O157 (3), O26 (4), O103 (5), and O111 (7). Forty seven isolates were further characterized by analysis of whole genome sequences to detect Shiga toxin gene (stx 1 and stx 2), intimin gene (eaeA) allelic variants and acquired virulence factors. These analyses collectively showed that surface waters from the region support highly diverse STEC populations that include strains with virulence factors commonly associated with human pathotypes. The present work served to characterize the microbiological hazard implied by STEC to support future assessments of risks to public health arising from non-agricultural and agricultural uses of surface water resources in the region.

Multi-Year Persistence of Verotoxigenic Escherichia coli (VTEC) in a Closed Canadian Beef Herd: A Cohort Study

“…The VT-immunoblot method (VT-IB) has been successfully used for the isolation of VTEC from enrichment cultures of ground beef ( Atalla et al, 2000 ), surface water samples ( Johnson et al, 2014 ; Nadya et al, 2016 ; Falardeau et al, 2017 ) and enriched cattle feces ( Karama et al, 2008 ). This study represents the first use for unenriched cattle feces.…”

“…Methods used for the detection and isolation of VTEC were similar to those described in Atalla et al (2000) , Karama et al (2008) , Johnson et al (2014) , Nadya et al (2016) , and Falardeau et al (2017) with modifications for unenriched fecal samples.…”

Occurrence, characterization, and potential predictors of verotoxigenic Escherichia coli, Listeria monocytogenes, and Salmonella in surface water used for produce irrigation in the Lower Mainland of British Columbia, Canada

“…With respect to weather, higher precipitation was shown to correlate with higher occurrence of VTEC O157 [ 22 ] and Salmonella [ 23 ] in Georgia. Similarly, precipitation three days prior to sampling was significantly correlated with the occurrence of VTEC O157 in Alberta [ 24 ], VTEC in British Columbia [ 25 ], and Salmonella in New York State [ 26 ]. Finally, pathogen occurrence has been observed to change over season, but not always consistently in different areas.…”

“…The occurrence of VTEC O157 was observed to be higher during the summer months in Alberta [ 27 ] and Georgia [ 22 ], but was more common during the winter in California [ 28 ]. In British Columbia, VTEC of any serotype was also most common during the winter [ 25 ]. More consistency has been observed for L .…”

“…To date, only one study has investigated the occurrence of VTEC in the surface waters of the Lower Mainland of British Columbia [ 25 ], and none has investigated the occurrence of L . monocytogenes or Salmonella .…”