Summary of Awards to Date

Integrated assessment of agronomic management practices on the interactions of soil and rhizosphere microbial communities with E. coli O157:H7.

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Sep. 1, 2008 - Aug. 31, 2011

Award Number


Funding Agency

Center for Produce Safety

Amount Awarded



Trevor Suslow, Ph.D.
University of California, Davis


Scow, K., and Six, J.


Food borne illnesses associated with consumption of leafy greens have increased noticeably in the last ten years with more than 20 outbreaks involving E. coli O157:H7 on lettuce, mixed leafy greens, and spinach. The consumption of spinach alone, over the last decade, has significantly increased from 1.6 pounds per person in the 1990's to over 2.4 pounds per person in 2005. That spinach consumption has increased, and therefore the proportional risk of sporadic illness (if levels of pathogen contamination have remained constant) is not surprising. This project addresses the persistence of enterohaemorrhagic E. coli on fresh spinach in the preharvest environment. It specifically focuses on the potential for survival and growth of E. coli O157:H7in a fluctuating and potentially competitive soil environment. The specific objectives will evaluate the influences of fertility management on the plant in relation to microbial community development and colonization of E. coli O157:H7 of under these agronomic practices. Comparisons of applied nitrogen concentration or nitrogen-form, in particular, are anticipated to reveal food safety risk factors of fresh spinach and other leafy greens. Fertility inputs effect changes in leaf morphology, potentially elevating risk due directly to changes in pathogen survival, attachment, growth, and internalization. These factors are directly involved in setting standards and `metrics' for replant timing and pre-harvest intervals that are especially critical for spinach and other mechanically harvested mini-greens and spring-mix, commodities.