USDA invests $5.5 million in fresh produce research.

The USDA is furthering its research on the safety of fresh produce. Nearly $5.5 million will support collaborative efforts aimed at identifying risk factors and preventive measures that can be taken to prevent E. coli O157:H7 contamination. Outbreaks of E. coli O157:H7 illness involving fresh lettuce or spinach have been associated with pre-harvest contamination.

The USDA-ARS and Cooperative State Research, Education, and Extension Service (CSRES) are providing the funding to ARS scientist Rob Mandrell and his collaborators at the University of California to continue their research in the Central Valley of California. Mandrell will address such issues as where E. coli O157:H7 originates, how it survives on the plant, and what factors lead to an increase in produce-related outbreaks. Potential risk factors include animals, land practices, packing and processing processes, and wildlife.

Additionally, the effort will include workshops and publications that can educate animal operators, natural resource managers and the public about animal diseases that can be transferred to humans, and how animal waste can contaminate water sources. There will be a review of beneficial management practices for maintaining and improving water runoff quality.

On a related front, it is hypothesized that vertebrate populations function as a key source of E. coli O157:H7 contamination of watersheds where lettuce and other leafy vegetables grow. In addition, climate, landscape attributes and irrigation practices may correlate with increased risks of E. coli O157 and commensal E. coli contamination. Mandrell and colleagues intend to sample the environment of leafy vegetable production in order to quantify environmental loading by vertebrate sources, characterize predisposing conditions for hydrological transport of E. coli to lettuce fields and identify the in-field mechanisms of lettuce contamination.

The researchers will conduct an in-depth longitudinal study that identifies the key biotic and abiotic processes that sufficiently load, then hydrologically link and disseminate, primary environmental reservoirs of E. coli within and between lettuce fields, resulting in bacterial contamination of this raw commodity. Samples and strains isolated will be analyzed by ARS researchers using multi-locus variable number tandem repeat analysis and pulsed field gel electrophorsis to characterize isolates for genetic differences, determine molecular epidemiologic linkages among samples isolated or obtained from public health collaborators, and thus pinpoint the mechanisms that link and disseminate vertebrate sources of E. coli O157:H7 within and between lettuce fields.

Further information. Robert Mandrell, USDA-ARS Western Regional Research Center, Room WAB200-B, 800 Buchanan St., Albany, CA 94710; phone: [phone]; fax: [phone]; email: [e-mail].