Start Date: Dec 16, 2010
End Date: Dec 15, 2015
Research to control Campylobacter in turkeys will be pursued by subfractionating, identifying and characterizing microbial species in turkey ceca which are potential Campylobacter antagonists. Cecal populations will be subfractionated in vivo by antibiotic applications and dexamethasone induced stress. Potentially useful species will initially be associated with Campylobacter reductions in vivo and confirmed in vitro by using co-cultures. Two other approaches for controlling Campylobacter will be tested: dietary additives (prebiotics and probiotics) and a prime-boost vaccination strategy using Campylobacter. jejuni surface membrane protein CjaA expressed in a recombinant strain of attenuated Salmonella. The commensal anaerobe Megasphaera elsdenii (M. elsdenii) will be used as an archetype intestinal bacterium to identify common antibiotic resistance genes and transfer mechanisms in the intestinal tract and to test M. elsdenii as a site for tetracycline resistance gene evolution in that ecosystem. In a probiotic type attempt, a mix of five antibiotic sensitive M. elsdenii strains will be used to block the transmission of antibiotic resistant strains from mother sow to offspring pigs. Various technologies will be used to assess the effects of alternatives to antibiotics (e.g. fermentation products) on swine performance and intestinal health. Technologies include intestinal microbiome analyses by QPCR-, phylotype census-, culture-based methods; metagenomic analyses of animal host gene expression (esp. immunome); and traditional immunological techniques. A variable heat stress model for swine will be developed and used to test diurnal heat cycle impacts on animal health and on colonization/shedding of foodborne pathogens such as Salmonella, as well as amelioration of the impacts by antibiotic alternatives. Immunotherapeutic measures (vaccine) will be examined for their impact on the swine immunome and Salmonella shedding. Other areas of research will include the influence of subinhibitory antibiotics on the production of Salmonella bacteriophages carrying fitness or virulence genes and on phage mediated gene transfer between Salmonella strains (transduction). These studies will be carried out with Salmonella Typhimurium strains in culture and in a mouse model. Functional metagenomics assays involving recombinant Escherichia coli and Salmonella strains containing reporter plasmids will be used to identify gene products which either affect Salmonella virulence or are inhibitory for Salmonella growth.