News Stories

THE ISSUE

Escherichia coli O157:H7 was found in spinach packaged in San Juan Bautista that was linked to the deaths of at least three people and more than 200 people who became ill in 2006. Foodborne illness outbreaks have also been linked to lettuce in the past. Growers and processors need to find out how the E. coli O157:H7 contamination occurred so they can take steps to prevent it from occurring again in fresh spinach or any other food crop.

WHAT UC IS DOING

UC campus-based scientists and specialists and county-based UC Cooperative Extension (UCCE) advisors are working with growers and livestock producers to study the biology, ecology, and possible sources of E. coli in agricultural systems including the postharvest phases of food handling. They are testing diverse environmental sources, irrigation water, soil, soil amendments, and plants for E. coli O157:H7.

UC Davis-based postharvest specialist Trevor Suslow has been working with Steve Koike, UCCE plant pathology advisor for Monterey and Santa Cruz counties, and other local farm advisors for the past five years on E. coli -related projects:

To establish a baseline of fecal indicators, they have conducted extensive testing of on-farm irrigation reservoirs and associated lettuce fields across the Salinas Valley over multiple seasons.

To assess the presence of E. coli, the scientists tested samples of soil from cropped fields -- including flood-impacted fields -- and irrigation and run-off water for enteric bacteria. To date, they have detected no evidence of viable E. coli O157:H7 in any samples.

They also tested samples of lettuce plants and didn’t detect E. coli O157:H7.

In their comparison of detection methods, the scientists found that commercial test kits routinely resulted in “false-positives” for identifying E. coli, particularly in manure, compost and soil.

They currently have funding to evaluate new methods for assessing irrigation water quality and to validate treatments for disinfecting the surface of leafy greens. They are seeking funding to examine survival and regrowth of the bacteria in soil and the potential for contamination via aerosol transfer from adjacent land activities.

Rob Atwill, UC Davis Cooperative Extension specialist and veterinarian, and Robert E. Mandrell, USDA-Agricultural Research Service, are co-principal investigators on a project studying the ecology and epidemiology of E. coli 0157:H7 in fresh produce production regions of the Salinas Valley. This $1.17 million grant is from the USDA Cooperative State Research, Education, and Extension Service - National Research Initiative (NRI) Competitive Grant Program. Since the recent E. coli outbreak was traced to spinach grown in San Benito County, project leaders have asked for an additional $600,000 to extend this project into that county. Royce Larsen, UCCE natural resources watershed advisor, is one of several UCCE advisors cooperating on the project.

The main questions the scientists will try to answer during this project include:

1) What are the sources? Do livestock contaminate water or nearby fields of fresh fruit or vegetables with E. coli O157:H7? What other wildlife species may be a potential source?

2) If animals are a source, what is the probability of them causing the contamination? How is E. coli transported? If livestock or wildlife are sources then multiple processes need to occur before contamination of leafy greens can happen:

• fecal (pathogen) loading in the environment (how much, what animals?)
• transport to water or through air
• survival or growth while in transport and reach the fields.

If wildlife defecate in the field or organic amendments (manure) are not fully treated, then direct contamination could occur.

The lettuce-E. coli project will examine livestock and wildlife in the Salinas Valley rangeland above the farmland, and wildlife that live near canals and on the periphery of vegetable fields on the valley floor to locate sources of E. coli O157:H7. The scientists will conduct an in-depth longitudinal study that identifies the key processes that sufficiently load, then link and disseminate E. coli O157:H7 within and between lettuce fields, resulting in bacterial contamination of leafy greens and other vegetables.

RESEARCH FUNDING

UC has requested $2 million in the FY 2008 federal budget for the creation of a new Fresh Produce Food Safety Research initiative, under the USDA Cooperative State Research, Education and Extension Services (CSREES). This statewide competitive research program will be administered by the UC Davis-based Western Institute for Food Safety and Security to advance scientific knowledge in the sources and causes of food-borne illnesses in fresh produce, and deliver this critical information to growers, food processors and government agencies. The industry has already committed over $4 million towards food safety research. In addition, Governor Schwarzenegger’s budget includes $2.1 million in funds for research and inspection activities.