Occurrence and potential predictors of verotoxigenic Escherichia coli (VTEC), Salmonella, and Listeria monocytogenes in surface water used for produce irrigation in the Lower Mainland of British Columbia, Canada
Bibliographic record
Abstract
Foodborne pathogens such as verotoxigenic Escherichia coli (VTEC), Salmonella, and Listeria monocytogenes may be present in surface waters, thus having the potential to contaminate fresh produce during crop irrigation. The objectives of this study were to determine the occurrence of VTEC, Salmonella, and L. monocytogenes in surface waters used for produce irrigation in the Lower Mainland of British Columbia, and to investigate potential predictors of their presence. Water samples (n = 223) were collected from three and four irrigation ditches in both the Serpentine and Sumas watersheds, respectively, between February 2015 and August 2016. VTEC colonies on water filters were detected using a verotoxin colony immunoblot developed for the detection of all VTEC serotypes, and isolates were confirmed via multiplex PCR for virulence genes vt1 and vt2. Detection of Salmonella and L. monocytogenes was completed using Health Canada Methods MFHPB-20 and MFHPB-30, respectively. Generic E. coli (EC) and fecal coliforms (FC) were enumerated using 3M™ Petrifilm™ Count Plates, and by membrane filtration with growth on m-FC agar with 0.01% rosalic acid; this was followed by transfer to nutrient agar containing 4-methylumbelliferyl-β-D-glucuronide. Meteorological data were collected from Environment Canada records, and agricultural data were collected from the British Columbia Agricultural Land Use Inventories. The most commonly occurring pathogen was L. monocytogenes (11.2%), followed by VTEC (4.93%), and Salmonella (2.68%). Pathogen recovery was more common in the Serpentine watershed (p < 0.05), especially during the winter and fall seasons (p < 0.05). Pathogen occurrence in these locations was correlated with FC (r = 0.431) and EC (r = 0.408), but only by using the membrane filtration method. Pathogens were still recovered when indicator concentrations were low. Pathogen occurrence was also correlated with the proximity to upstream livestock (rs = -0.886) and the level of precipitation the day before sample collection (r = 0.203). In conclusion, VTEC, Salmonella, and L. monocytogenes are present in surface waters used for irrigation in the Lower Mainland of British Columbia. There is potential to predict their presence, but further research is required to confirm factors affecting pathogen occurrence, which entail longer sampling times and increased sampling locations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".