Project Number: 8042-32420-005-00
Start Date: Apr 01, 2011
End Date: Mar 31, 2016
Mechanisms of introduction and transfer of pathogens on fresh produce (lettuce, spinach, tomatoes, leafy greens) at the farm level will be investigated. Growth and survival patterns of avirulent strains of Enterohemorrhagic E. coli (EHEC) and Salmonella will be evaluated in composted manure with different pile size and configuration. Deposition of airborne-microbes onto fresh produce will be evaluated during different times of the year to determine proximity distance between fields and suspected nearby source of contamination. The role of insect vectors in transmission of pathogens to fresh produce will be studied and biocontrols will be used as a potential deterrent to insects. Bacterial analysis will include the use of microbial culture and molecular methods to detect target pathogens in samples. Persistence of EHEC and Salmonella on fresh produce will be determined when these pathogens are introduced at different levels via irrigation water. Clostridium perfringens and coliphages will be evaluated as suitable indicators for fecal contamination of irrigation water. Zero-valent iron (ZVI) columns will be evaluated as an intervention for removing pathogens from irrigation water. The role of specific virulence and stress factors on the ability of EHEC to attach and persist on fresh produce will be determined. Wild-type and curli- and cellulose-deficient strains of EHEC and Salmonella will be evaluated for their attachment and biofilm formation on fresh produce; biofilm formation on foliar surfaces will be determined by confocal laser scanning microscopy (CLSM). Existing and novel new antimicrobial wash treatments which remove biofilm from foliar surfaces will be evaluated. The effect of tomato dump tank management parameters on the probability and extent of Salmonella infiltration will be determined; the infiltration pattern will be determined by CLSM. The effect of the wash-cut sequence on pathogen cross-contamination during cutting and washing of fresh produce will be investigated. To minimize the chlorine degradation of wash water used for fresh produce wash, chlorine stabilizer will be used in wash water to evaluate its effect on chlorine stability of wash water and additional pathogen reduction on fresh produce. Pathogen growth and virulence as impacted by temperature abuse at a retail level and modified atmosphere packaging (MAP) of fresh produce will be evaluated.