Change in the Structure of Escherichia coli Population and the Pattern of Virulence Genes along a Rural Aquatic Continuum

Abstract

The aim of this study was to investigate the diversity of the Escherichia coli population, focusing on the occurrence of pathogenic E. coli, in surface water draining a rural catchment. Two sampling campaigns were carried out in similar hydrological conditions (wet period, low flow) along a river continuum, characterized by two opposite density gradients of animals (cattle and wild animals) and human populations. While the abundance of E. coli slightly increased along the river continuum, the abundance of both human and ruminant-associated Bacteroidales markers, as well as the number of E. coli multi-resistant to antibiotics, evidenced a fecal contamination originating from animals at upstream rural sites, and from humans at downstream urban sites. A strong spatial modification of the structure of the E. coli population was observed. At the upstream site close to a forest, a higher abundance of the B2 phylogroup and Escherichia clade strains were observed. At the pasture upstream site, a greater proportion of both E and B1 phylogroups was detected, therefore suggesting a fecal contamination of mainly bovine origin. Conversely, in downstream urban sites, A, D, and F phylogroups were more abundant. To assess the occurrence of intestinal pathogenic strains, virulence factors [afaD, stx1, stx2, eltB (LT), estA (ST), ipaH, bfpA, eae, aaiC and aatA] were screened among 651 E. coli isolates. Intestinal pathogenic strains STEC O174:H21 (stx2) and EHEC O26:H11 (eae, stx1) were isolated in water and sediments close to the pasture site. In contrast, in the downstream urban site aEPEC/EAEC and DAEC of human origin, as well as extra-intestinal pathogenic E. coli belonging to clonal group A of D phylogroup, were sampled. Even if the estimated input of STEC (Shiga toxin-producing E. coli) – released in water at the upstream pasture site – at the downstream site was low, we show that STEC could persist in sediment. These results show that, the run-off of small cattle farms contributed, as much as the wastewater effluent, in the dissemination of pathogenic E. coli in both water and sediments, even if the microbiological quality of the water was good or to average quality according to the French water index.

Landscape, Water Quality, and Weather Factors Associated With an Increased Likelihood of Foodborne Pathogen Contamination of New York Streams Used to Source Water for Produce Production

“…In the present study, we found evidence of a strong, positive association between ruminant FST markers (Rum2Bac) and eaeA-stx codetection, and between human FST markers (HF183) and Salmonella isolation. In general, these findings are consistent with past studies that found strong associations between ruminant fecal contamination and detection of pathogenic E. coli markers (Walters et al, 2007;Petit et al, 2017), and between human fecal contamination and Salmonella detection (Marti et al, 2013;Liang et al, 2015;Stea et al, 2015). For example, Stea et al (2015) found that the odds of detecting molecular makers for Salmonella in Nova Scotia surface water samples was 2.2 times greater when human FST markers were present as opposed to when human FST markers were not detected.…”

Niche preference ofEscherichia coliin a peri-urban pond ecosystem

“…The prevalance of B1 and E, and some B2 in water, water plant and sediment was consistant with previous studies where B1 have been interpreted as generalists and harbor traits linked to plant association, whereas B2 strains are associated more with animals [53,54]. Phylogroup distribution within the E. coli population in both water and superficial sediments showed spatial variation [31]. It has also been reported that phylogenetic groups are adaptable and genotypically influenced by changes in environmental conditions, however phylogroup B1 isolates seem to persist in water [8,55].…”

“…This pond is located between the edge of town, a nature park, and a cattle pasture, and surrounded by dense scrub and trees, rarely visited by humans. Water (31), sediment (27), water plant (35), and snail samples (20) were collected from the pond, and bovine feces (7) was collected from the adjoining cattle pasture. Samples were placed into sterile 50 mL conical screw cap tubes, brought to the laboratory on ice and processed on the same day.…”

“…Certain strains of E. coli present in the environment also appear to have become naturalized, and to have distinct genotypes when compared to strains associated with animal hosts [9,21]. Previous studies have suggested that there is a relationship between genotypes of E. coli found among specific animal hosts and the geographic location from which they were isolated [21,30,31]. The genetic differences between populations are a consequence of continued evolutionary success due to their survival and adaptation in different environments [32].…”

Identification of Factors Affecting Fecal Pollution in Beaver Lake Reservoir

“…Agricultural runoff into surface waters used for recreational activities and drinking water sources is a concern for watersheds around the world (Jokinen et al, 2012; Haack et al, 2015, 2016; Petit et al, 2017). Here, E. coli presence and elevated concentrations were significantly associated with the WR site, highlighting the potential impact of surface runoff from the upper portion of the WR dominated by hardwood forests (59%), pasture (30%), and cropland (9%) compared with just 4% urban land use (ANRC, 2012).…”