Summary of Awards to Date

Ecology and Epidemiology of Escherichia Coli O157:H7 in fresh produce production regions of Salinas, California.

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Sep. 30, 2006 - Sep. 30, 2010

Award Number


Funding Agency

Center for Produce Safety

Amount Awarded



Robert E. Mandrell, Ph.D.
Western Regional Research Center, Albany, CA


Consumption of fresh fruits and vegetables is growing in the United States, however, this trend coincides with produce outbreaks. Since 1995, 16 outbreaks of Escherichia coli O157:H7 (EcO157) associated with fresh lettuce or spinach have occurred; 7 outbreaks were traced to the Salinas, California. Intensive investigation of 3 recent outbreaks implicated a single farm as a supplier of contaminated lettuce, indicating pre-harvest contamination. Our hypothesis is that key biotic and abiotic processes hydrologically link primary reservoirs of EcO157, resulting in bacterial contamination of produce. The goal is to develop and implement science-based strategies to prevent on-farm contamination of produce. We propose to sample extensively vertebrate animal feces, creek/ditch and irrigation water, soil and produce for commensal and EcO157, and use epidemiological approaches to determine if: (1) vertebrate populations are sources of EcO157 contamination of watersheds; (2) climate, landscape attributes, and irrigation management practices correlate with increased risk of contamination; and (3) in-field contamination of lettuce with EcO157 is associated with management production practices and environmental risk factors in the Salinas. The information obtained from this study will be used to inform produce growers about strategies to prevent pre-harvest microbial contamination, to educate the livestock community about potential impacts of rangeland runoff on watersheds and down-stream stakeholders, and to develop effective management practices for improving water quality.