EPIDEMIOLOGY AND ECOLOGY OF E. COLI O157:H7 IN THE SALINAS VALLEY

We hypothesize that vertebrate populations (especially cattle and wild birds) function as a key source of E. coli O157:H7 (EcO157) contamination of watersheds where lettuce and other leafy vegetables are grown; that climate, landscape attributes, and irrigation practices correlate with increased risks of EcO157 and commensal E. coli contamination; and in-field contamination of lettuce plants with EcO157 relates to combinations of production practices and environmental risk factors in the Salinas Valley. The major objectives of this proposal are to (1) quantify environmental loading by vertebrate sources, (2) characterize predisposing conditions for hydrological transport of EcO157 and E. coli to lettuce fields, (3) determine if concentrations of non-O157 E. coli predict an increased risk of contamination with EcO157 in water, (4) identify the in-field mechanism(s) of contamination of lettuce, (5) create a molecular subtyping database of EcO157 strains to characterize the genetic relatedness of environmental and outbreak-associated isolates, and (6) develop and disseminate educational materials for growers of fresh produce and the livestock community about microbial water quality, potential impacts on down-stream stakeholders, and effective BMPs for improving water quality.