Purpose: The objective of this study was to determine the effect of farm management and environmental factors on the preharvest spinach contamination with generic E. coli as an indicator of fecal contamination.
Methods: A repeated cross-sectional study was conducted by visiting spinach farms up to four times per growing season over a period of two years (2010 and 2011). A total of 955 spinach samples were collected from 12 spinach farms in Colorado and Texas as representative states of the Western and Southwestern United States, respectively. Farmers were surveyed about farm-related management and environmental factors using a questionnaire. Associations between the prevalence of generic E. coli in spinach and farm-related factors were assessed using a multivariable logistic regression model including random effects for farm and farm visit.
Results: Overall, 6.6% of spinach samples were positive for generic E. coli. Significant risk factors for spinach contamination with generic E. coli were proximity (within 10 miles) of a poultry farm, the use of pond water for irrigation, the period since planting spinach greater than 66 days, farming on fields previously used for grazing, production of hay before spinach planting, and the farm location in the Southwestern United States. The presence of generic E. coli was significantly reduced when the irrigation lapse time was greater than 5 days, by the use of portable toilets, training to use portable toilets, and use of hand-washing stations.
Significance: To our knowledge, this is the first report of an association between field workers’ personal hygiene and produce contamination with generic E. coli at the preharvest level. Collectively, our findings support that practicing good personal hygiene and other good farm management practices may reduce produce contamination with generic E. coli at the preharvest level.