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Microbiology and Control of Pathogen Contamination on Fresh and Fresh-Cut Produce


<UL> <LI>Determine how pathogens are introduced into the environment where fresh and fresh-cut lettuce is grown, harvested, and undergoes postharvest handling. <LI> Determine the persistence and survival of pathogens in the environment during growing, harvesting, postharvest handling, and/or processing of fresh and fresh-cut lettuce. <LI>Determine the mechanism(s) of transference of pathogens to fresh and fresh-cut lettuce edible plant surfaces during growing, harvest, postharvest handling and processing operations. <LI>Determine the persistence and survival of pathogens in lettuce during growing, harvest, postharvest handling and/or processing.

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Approach: Extrinsic factors will be evaluated to determine their effect on survival of EHEC foodborne pathogens. Conditions will be designed so that they resemble actual pre-harvest, farming, and post-harvest practices. Various feces types (poultry, cattle, swine) will be inoculated with either low or high levels of pathogens and then used in manure to be applied to crops or plants. Soil can then be tested for populations of various pathogens. Various portions of crops (leaves, stems, edible portions) can be analyzed for the presence of pathogens to determine if foodborne pathogens can act as either endophytes or epiphytic organisms or be taken up systematically through plants. This may help determine the behavior of pathogens in organic farming environments through a harvesting season. Both organic (manure that comes from animals not receiving antibiotic and growth hormone treatments) and non-organic animals (manure from conventionally raised animals) will be evaluated. Microbial communities in soil will be profiled to determine if a "bloom" effect takes place after the application of either a) chemical fertilizers containing nitrogen, phosphorus and potassium or b) organic compost. Molecular techniques (16S rRNA) will be employed to identify strains, and the populations of EHEC pathogens within those communities. These efforts would help determine if crops raised organically have different microbial communities than conventionally raised crops. Biofilms of single and multi-species will be established on food contact surfaces to determine if pathogens can be transferred from produce or fresh-cut produce from these surfaces. Differences in transferred populations from inoculated non-contact surfaces to fresh or fresh-cut surfaces will be examined. Commonly employed microbial interventions and/or sanitation measures in addition to novel interventions will then be used to determine if biofilms from food contact surfaces and those cells transferred to produce can be killed. Real time PCR assays will be developed for the detection of bacterial pathogens on produce and on food contact surfaces. The assays will be optimized to increase the sensitivity and the specificity of PCR reactions. This will determine if there are inhibitors to PCR reactions (low pH, excess metal ion concentration, and degrading enzymes) that could interfere with detection in produce samples. PCR assays may provide more sensitive detection of specific pathogens in a multi-species biofilm where the use of traditional culture methods may not be suitable for detection.

Nou , Xiangwu; Patel, Jitu; Sharma, Manan; Solomon, Morse
USDA - Agricultural Research Service
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