The Effects of Current Agricultural Practices on the Survival and Transfer of Shiga Toxin Producing Escherichia Coli and Salmonella on Small Multi-functional Farms in Alabama

Non-Technical Summary: <br/>Alabama has unique weather conditions compared to the other parts of the United States. It has very hot summers and mild winters with copious precipitation throughout the year. Alabama receives an average of 56 inches (1,400 mm) of rainfall annually and enjoys a lengthy growing season of up to 300 days in the southern part of the state. The average annual temperature is 64 F. In the state of Alabama, there are significant amount of small farms. Those farmers have fewer cattle compared to huge commercial ranches and they grow vegetables and fruits on the farms to meet the community needs and make profit. In this research program, studies will be planned to provide additional information to our current knowledge on "the effects of feed, management, and stresses on GI tract microflora and shedding of pathogenic bacteria", "influence of weather conditions on the survival and transfer of pathogens on farm" and "molecular survival mechanisms of STEC and Salmonella". The outcomes are expected to fill some of the gaps regarding the pre-harvest food safety control. Most importantly, this research program will be dedicated to help the small farmers in the state of Alabama to establish efficient and feasible intervention methods to enhance their product safety. Due to the happening of several multi-state foodborne outbreaks, consumers are now paying more attention to local foods and they want to be able to put a face onto their products. By having more efficient intervention and management strategies in place, both the farmers and consumers will be more confidence about their food, and ultimately, the farmers can make more profit for living.
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Approach:<br/>
1. The effects of feed changes/management practices/transportation stresses on the GI tract microbial diversity and the shedding of STEC and Salmonella. A total of 120 calves born around November 2011 will be brought to the E.V. Smith center in Spring 2012. Half of the group will be fed with wet diet while the other half will be fed with dry diet. These calves will stay on the controlled diet for 45 days before they are taken for a 21-h road trip. For the microbial part, fecal, hide and environmental samples at different time points will be collected. The time points are divided into two groups, "diet treatments" and "road-trip stresses". The baseline will be built based on samples collected when calves get their first vaccination (May 2012). After the initial sampling, fecal, hide and environmental samples will be collected in the middle of the 45-day diet treatment and at the end of 45-day diet treatment. Total microbial profile as well as the present of STEC and Salmonella will be studied. Environmental samples collected from the farm will include water, feed and bedding materials and the purpose is to find the potential of cross-contamination routes.
<P>2. The influence of weather conditions on transfer, survival, growth and recovery of foodborne pathogens on farms. In this study, uidA-based PCR and DGGE will first be used to group the E. coli fingerprints from sheep, cattle and rabbit fecal samples, soil samples and the pond (including water runoffs)collected from small farms. The uidA gene is chosen because this gene encodes the 1-glucuronidase enzyme and is detected in 97.7% of 435 E. coli isolates from treated and raw water sources by DNA-DNA hybridization. Once the fresh produce gets transplanted to the field, the total E. coli diversity on produce leaves will be monitored. The goal is to understand the transfer of E. coli communities before and after weather changes. Both the real-time PCR and traditional plating methods will be used to evaluate the quantity changes of the total E. coli communities. 3. The molecular survival mechanism of STEC and Salmonella and their dynamic pathogenicity. Research program will be developed to investigating the function of E. coli O157:H7 extracellular structures and comparing the different roles of these extracellular structures between E. coli and Salmonella. Extracellular structures are chosen because they are the first barriers that protect cells from environmental stresses. Microarrays and real-time PCR will be used to monitor the expression of extracellular structural genes under various stresses as well as the expression of pathogenic genes. In vitro studies will be conducted via the collaboration with Veterinary school on campus to examine the effects of formed hyper-virulent strains.