Transfer of Escherichia coliO157:H7 from Simulated Wildlife Scat onto Romaine Lettuce during Foliar Irrigation

Atwill, Edward R.; Chase, Jennifer; Oryang, David; Bond, Ronald F.; Koike, S. T.; Cahn, Michael; Anderson, Maren; Mokhtari, Amirhossein; Dennis, Sherri

doi:10.4315/0362-028x.jfp-14-277

Cited by 49 publications

(74 citation statements)

References 18 publications

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“…Irrigation water has the potential to contaminate leafy greens if there is direct contact of water containing human pathogens with edible portions of leafy greens or indirectly by means of water-to-soil and soil-to-leafy greens contact (12). Even if the irrigation water is not contaminated, sprinkler irrigation can result in contamination of plants as pathogens present in the soil can be transferred from soil to plant through splashes created by irrigation water (15). Water with a bigger droplet size will have a higher kinetic energy and will maximize the erosive forces of irrigation water on contaminated soil or feces (15).…”

Section: Discussionmentioning

confidence: 99%

“…Even if the irrigation water is not contaminated, sprinkler irrigation can result in contamination of plants as pathogens present in the soil can be transferred from soil to plant through splashes created by irrigation water (15). Water with a bigger droplet size will have a higher kinetic energy and will maximize the erosive forces of irrigation water on contaminated soil or feces (15).…”

Section: Discussionmentioning

confidence: 99%

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A System Model for Understanding the Role of Animal Feces as a Route of Contamination of Leafy Greens before Harvest

Mishra

Pang

Buchanan

et al. 2017

Appl Environ Microbiol

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The majority of foodborne outbreaks in the United States associated with the consumption of leafy greens contaminated with Escherichia coli O157:H7 have been reported during the period of July to November. A dynamic system model consisting of subsystems and inputs to the system (soil, irrigation, cattle, wild pig, and rainfall) simulating a hypothetical farm was developed. The model assumed two crops of lettuce in a year and simulated planting, irrigation, harvesting, ground preparation for the new crop, contamination of soil and plants, and survival of E. coli O157:H7. As predicted by the baseline model for crops harvested in different months from conventional fields, an estimated 13 out of 257 (5.05%) first crops harvested in July would have at least one plant with at least 1 CFU of E. coli O157:H7. Predictions indicate that no first crops would be contaminated with at least 1 CFU of E. coli O157:H7 for other months (April to June). The maximum E. coli O157:H7 concentration in a plant was higher in the second crop (27.10 CFU) than in the first crop (9.82 CFU). For the second crop, the probabilities of having at least one plant with at least 1 CFU of E. coli O157:H7 in a crop were predicted as 15/228 (6.6%), 5/333 (1.5%), 14/324 (4.3%), and 6/115 (5.2%) in August, September, October, and November, respectively. For organic fields, the probabilities of having at least one plant with Ն1 CFU of E. coli O157:H7 in a crop (3.45%) were predicted to be higher than those for the conventional fields (2.15%).IMPORTANCE This study is the first attempt toward developing a mathematical system model to understand the pathway of E. coli O157:H7 in the production of leafy greens. Results of the presented system model indicate that the seasonality of outbreaks of E. coli O157:H7-associated contamination of leafy greens was in good agreement with the prevalence of this pathogen in cattle and wild pig feces in a major leafy greens-producing region in California. On the basis of comparisons among the results of different scenarios, it can be recommended that the concentration of E. coli O157:H7 in leafy greens can be reduced considerably if contamination of soil with wild pig and cattle feces is mitigated.KEYWORDS leafy greens, Escherichia coli O157:H7, outbreaks, system model, animal feces T he "Dietary Guidelines for Americans, 2010" recommends that adults and children eat a variety of fruits and vegetables in order to lower the risk of chronic diseases and to achieve and maintain a healthy weight (1, 2). While leafy vegetables are an important part of a healthy and nutritious diet, they are usually consumed raw; thus, any leafy vegetables with contaminated pathogens have the potential to cause food-

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A System Model for Understanding the Role of Animal Feces as a Route of Contamination of Leafy Greens before Harvest

Mishra

Pang

Buchanan

et al. 2017

Appl Environ Microbiol

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“…Samples were then held at 6°C with no shaking. Five µL from each dilution was streaked onto CHROMagar E. coli followed by incubation for 24 hr at 37°C (Atwill et al, ). MPN series cell densities were calculated based on dilution to extinction using an MPN Calculator (Curiale, ).…”

Section: Methodsmentioning

confidence: 99%

“…Samples were then held at 6°C with no shaking. Five µL from each dilution was streaked onto CHROMagar E. coli followed by incubation for 24 hr at 37°C (Atwill et al, 2015).…”

Section: Enumeration Of Generic Escherichia Coli In Soil Samplesmentioning

confidence: 99%

Persistence of Escherichia coli in the soil of an organic mixed crop‐livestock farm that integrates sheep grazing within vegetable fields

Patterson

Navarro-González

Jay-Russell

et al. 2018

Zoonoses and Public Health

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Mixed crop-livestock farms (MCLF) integrate livestock and crops using their animals to graze crop residues and/or cover crops. MCLF are considered sustainable because grazing and the manure deposited by livestock enhance soil fertility and recycles farm nutrients. However, livestock manure may introduce enteric foodborne pathogens to the soil, which could contaminate fresh produce. Organic farmers in the United States follow the USDA National Organic Program (NOP) standards, which require 90 or 120 days between incorporating raw manure into the soil and harvest. Although not specifically addressed in NOP, organic farmers using grazing within production fields may also use this standard. The objectives of this study were to generate preharvest data to assess the die-off of generic Escherichia coli (E. coli) in the soil, after cover crops were grazed by sheep; and assess the genetic relatedness of generic E. coli isolates between soil and sheep faecal samples. We conducted a repeated observational study to evaluate the persistence of generic E. coli, as an indicator of faecal contamination and surrogate for STEC, in the soil of two fields (A and B) on an organic MCLF. Results showed a 3.70 log reduction in mean generic E. coli concentration MPN in the soil of field A from the highest of 3.70 log MPN/g on 48 day postsheep grazing (DPS) to -0.70 log MPN/g on 139 DPS. Field B showed a 3.51 log reduction in mean generic E. coli concentration in the soil from the highest mean of 3.51 log MPN/g on 14 DPS to the lowest mean -0.35 log MPN/g on 112 DPS. STEC prevalence in the sheep flock was 4.17% (1/24). Closely related generic E. coli strains were found between soil and faecal samples. Developing research-based waiting periods between grazing and harvest is important to inform best practices for farmers and food safety regulators.

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“…While there have been an abundance of studies to model bacterial survival kinetics (Chase et al, 2017, Salazar et al, 2017), transfer dynamics (Atwill et al, 2015), and preharvest risk factors (Pagadala et al, 2015) linked to raw produce consumption (Ibekwe et al, 2005; Pachepsky et al, 2016; Tian et al, 2012), relatively little is known about the potential risk inherent in agricultural water supplies.…”

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confidence: 99%

Spatiotemporal Variability in Microbial Quality of Western US Agricultural Water Supplies: A Multistate Study

et al. 2018

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In 2011, the US Congress passed the Food Safety Modernization Act, which tasks the US Food and Drug Administration to establish microbiological standards for agricultural water. However, little data are available for the microbiological quality of surface water irrigation supplies. During the 2015 irrigation season, we conducted a baseline study on the microbial water quality of large irrigation districts in California (n = 2) and Washington (n = 4). Monthly samples (n = 517) were analyzed for bacterial indicators (fecal coliforms, enterococci, and Escherichia coli) and pathogens (Salmonella spp., E. coli O157, and non‐O157 Shiga toxin‐producing E. coli [STEC]). Although there was a high degree of variability (μ ± SD = 59.13 ± 106.0), only 11% of samples (56/517) exceeded 126 colony‐forming units (CFU) 100 mL−1, and only six samples exceeded 410 CFU 100 mL−1. Two volumes of water were collected for pathogen analysis (1 L and 10 L); prevalence of Salmonella in 10‐L samples (68/149) was nearly double of that found in 1‐L samples (132/517). We found STEC during ∼9% of sampling events (58/517); serotypes O26 and O45 were the most common at 31 and 26%, respectively. Pathogens were not associated with exceedance of the regulatory threshold, yet the odds of detecting Salmonella increased approximately threefold (odds ration [O.R.] = 3.14, p < 0.0001) for every log increase in turbidity. Microbiological outcomes were highly district‐specific, suggesting drivers of water quality vary across spatiotemporal scales. The true risk of contamination of produce from irrigation water supplies remains unknown, along with the optimal monitoring strategy to improve food safety. Core Ideas Western US irrigation water supplies rarely exceed FDA agricultural water standards. Indicator bacteria are not predictive of pathogen prevalence or concentration. Prevalence of pathogens in irrigation water is higher than previously reported. Odds of detecting Salmonella improved >270% with an increase in sample volume. More research is needed to provide science‐based guidance to the produce industry.

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Transfer of Escherichia coliO157:H7 from Simulated Wildlife Scat onto Romaine Lettuce during Foliar Irrigation

Cited by 49 publications

References 18 publications

A System Model for Understanding the Role of Animal Feces as a Route of Contamination of Leafy Greens before Harvest

A System Model for Understanding the Role of Animal Feces as a Route of Contamination of Leafy Greens before Harvest

Persistence of Escherichia coli in the soil of an organic mixed crop‐livestock farm that integrates sheep grazing within vegetable fields

Spatiotemporal Variability in Microbial Quality of Western US Agricultural Water Supplies: A Multistate Study

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