Submitted to: Journal of Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2011
Publication Date: 7/1/2011
Citation: Berry, E.D., Wells, J. 2011. Soil solarization reduces Escherichia coli O157:H7 on cattle feedlot pen surfaces [abstract]. Journal of Food Protection. 74(Supplement A):80. Interpretive Summary:
Technical Abstract: Introduction: Soils at the feedlot pen surface are a source for transmission of Escherichia coli O157:H7, and therefore a target for control measures to reduce this pathogen in cattle. Soil solarization is a preplanting technique used in food and ornamental crop production, which utilizes solar energy to heat the soil and inactivate plant pathogens, nematodes, weeds, and weed seeds. Purpose: The objective of this study was to determine the ability of soil solarization to reduce E. coli O157:H7 from feedlot pen surface soils. Methods: A feedlot pen was identified in which E. coli O157:H7 was both highly prevalent and evenly distributed in the surface soils. Forty 10×10-ft. plots were randomly assigned such that 5 plots of solarization times of 0, 1, 2, 3, 4, 6, 8 and 10 weeks were examined. Plots were covered with 12×12-ft. sheets of clear 6 mil polyethylene. At each sampling, 5 soil samples were collected from each of the 10 plots (5 solarized and 5 unsolarized plots; n = 25). E. coli concentrations on CHROMagar ECC and E. coli O157:H7 presence by immunomagnetic separation and plating were determined for each soil sample. Results: Initial percentages of E. coli O157:H7-positive samples in solarized and unsolarized plots were 80 and 84%, respectively, and did not differ (P > 0.05). E. coli O157:H7 was no longer detectable by 8 weeks of solarization, but was still detected in unsolarized soils at 10 weeks. The average initial concentration of E. coli in soils was 5.56 log CFU/g, and did not differ between treatments (P > 0.05). There was a rapid 2.0-log decrease of E. coli after 1 week of solarization, and >3.0-log reduction of E. coli by week 6 of solarization (P < 0.001). E. coli concentrations remained unchanged in unsolarized soils after 10 weeks (P > 0.05). Average daily maximum temperatures were 10 to 12 degrees higher for solarized soils compared to unsolarized soils, and reached temperatures as high as 55°C. Significance: Because soil solarization effectively reduces E. coli O157:H7 from feedlot pen surface soils, it may be useful for reducing the transmission and persistence of this pathogen among cattle and the production environment. In addition, this technique may have application for remediation of E. coli O157:H7-contaminated soils used to grow food crops.