title: Baseline and storm event monitoring of Bacteroidales marker concentrations and enteric pathogen presence in a rural Canadian watershed.
abstract: Bacteroidales 16S rRNA gene markers were evaluated for their use as a microbial source tracking tool in a well characterized 750 ha agricultural watershed in Nova Scotia, Canada. Water quality monitoring was conducted following the validation of host-specific and universal Bacteroidales (AllBac) markers for their proficiency in this particular geographic region, which provided further evidence that these markers are geographically stable. Increasing Escherichia coli concentrations were positively correlated (p < 0.01) with concentrations of the AllBac marker in water samples, suggesting that this universal marker is more suited as a positive DNA control rather than as an indicator of recent fecal contamination. Ruminant (BacR) and bovine (CowM2) specific marker detection was associated with increased runoff due to precipitation in sub-watersheds putatively impacted by cattle farming, demonstrating that the BacR and CowM2 markers can be used to detect the recent introduction of fecal matter from cattle farming activities during rainfall events. However, the human associated marker (BacH) was only detected once in spite of numerous on-site residential wastewater treatment systems in the watershed, suggesting that this assay is not sensitive enough to detect this type of human sewage source. E. coli O157:H7 and Salmonella spp. DNA was not detected in any of the 149 watershed samples; however, 114 (76.5%) of those samples tested positive for Campylobacter spp. No significant correlation (p > 0.05) was found between Campylobacter spp. presence and either E. coli or AllBac marker levels. Further studies should be conducted to assess the origins of Campylobacter spp. in these types of watersheds, and to quantify pathogen cell numbers to allow for a human health risk assessment.
authors.affiliation: Department of Process Engineering and Applied Science, Dalhousie University, 1360 Barrington Street, Halifax, NS, Canada B3H 4R2.
authors.forename: C M
authors.initials: CM
authors.lastname: Ridley
authors.affiliation: Department of Process Engineering and Applied Science, Dalhousie University, 1360 Barrington Street, Halifax, NS, Canada B3H 4R2. Electronic address: jamiesrc@dal.ca.
authors.forename: R C
authors.initials: RC
authors.lastname: Jamieson
authors.affiliation: Department of Process Engineering and Applied Science, Dalhousie University, 1360 Barrington Street, Halifax, NS, Canada B3H 4R2.
authors.forename: L
authors.initials: L
authors.lastname: Truelstrup Hansen
authors.affiliation: Department of Biology, University of Regina, LB 244, 3737 Wascana Parkway, Regina, SK, Canada S4S 0A2.
authors.forename: C K
authors.initials: CK
authors.lastname: Yost
authors.affiliation: Agriculture and Agri-Food Canada, Atlantic Food and Horticulture Research Centre, 32 Main Street, Kentville, NS, Canada B4N 1J5.
authors.forename: G S
authors.initials: GS
authors.lastname: Bezanson
mesh_terms: D000818:Animals; D000829:Animals, Domestic / Q000382:microbiology; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification; D041963:Bacteroidetes / Q000235:genetics / Q000302:isolation & purification*; D015415:Biomarkers / Q000032:analysis; D002417:Cattle; D004269:DNA, Bacterial / Q000235:genetics; D004784:Environmental Monitoring; D005243:Feces / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D008322:Mammals / Q000382:microbiology; D009674:Nova Scotia; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011891:Rain; D014871:Water Microbiology; D060753:Water Quality; D060986:Water Wells / Q000382:microbiology*
chemical_list: D015415:Biomarkers; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: Bacteroidales; Campylobacter; Host-specific markers; Microbial source tracking (MST); Rural agricultural watershed