Researchers Pinpoint Factors Influencing Spinach E. coli Contamination

A new research report about E. coli contamination on spinach has been published in the July 2013 issue of Applied and Environmental Microbiology. Scientists found that contamination is “strongly influenced” by the time elapsed since the last irrigation, workers’ personal hygiene and what the field was used for before the spinach was planted.

In February 2013, Taylor Farms spinach was recalled for E. coli contamination, and late last year, 33 people were sickened in a multistate outbreak of E. coli O157:H7 linked to organic spinach. Another E. coli outbreak that sickened 200 people happened in 2006.

Researchers studied spinach farms up to four times per growing season over a period of two years in this study. They pulled 955 spinach samples from 12 farms in Colorado and Texas. They found that 6.6% of spinach samples were positive for genetic E. coli. The most significant risk factors for contamination were proximity of a poultry farm, the use of pond water for irrigation, a greater than 66-day period since the planting of spinach, farming on fields that were previously used for grazing, the production of hay before spinach planting, and farm location in the southwestern United States.

They also found that contamination was significantly reduced if the plants were harvested more than five days after the last irrigation, and when workers were trained in food safety rules, such as hand-washing stations and the use of portable toilets. The scientists believe that controlling these factors could be cost-effective strategies to control produce contamination.