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An investigation of Salmonella spp. in Ontario nursery pigs and the impact of flavophospholipol on Salmonella and the porcine microbiota

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Title: An investigation of Salmonella spp. in Ontario nursery pigs and the impact of flavophospholipol on Salmonella and the porcine microbiota
Author: Nair, Saranya
Department: Department of Population Medicine
Program: Population Medicine
Advisor: Friendship, RobertFarzan, Vahab
Abstract: Salmonella spp. (Salmonella) in nursery pigs is challenging as it can promote the maintenance and circulation of the bacteria through all stages of pork production. Flavophospholipol, an antibiotic, may have the ability to reduce Salmonella in swine, as well as alter the gut microbiota in favour of beneficial bacteria by inhibiting pathogenic bacteria like Salmonella. Thus, the objectives of this thesis were: (i) to identify nursery barns with an active Salmonella infection and to determine the risk factors associated with an active Salmonella infection, and (ii) to evaluate the impact of flavophospholipol on Salmonella and the fecal microbiota of nursery pigs challenged with Salmonella Typhimurium. Serological and bacteriological methods were used to identify active Salmonella infections on Ontario nursery cohorts. Approximately 80% (37/46) of nurseries were found positive either using serological or bacteriological methods or both. Findings revealed that using both screening techniques in parallel, improved the sensitivity of identifying an active Salmonella infection on a nursery cohort. A logistic regression was used to assess risk factors associated with an active Salmonella infection in nursery cohorts. However, examination of risk factors didn't identify why the negative farms were different from the others, but this warrants further study. Second, an experimental study was conducted to assess the impact of in-feed flavophospholipol on Salmonella in weaned pigs challenged with Salmonella Typhimurium over 36 days. Using next-generation sequencing, the fecal porcine microbiota was studied in a subset of these weaned pigs receiving in-feed flavophospholipol compared to those receiving a non-medicated diet before and after challenge with S. Typhimurium. Medicating nursery diets with flavophospholipol at 4 ppm did not appear to reduce Salmonella infection (shedding, tissue, antibody response) in nursery pigs. With regards to the fecal porcine microbiota, results demonstrated a significant increase in phylum Proteobacteria (P=0.001) and decrease in Firmicutes (P=0.012) and genus Roseburia (P=0.003) in the treated pigs suggestive of possible microbial dysbiosis. In conclusion, based on these findings, it is difficult to conclude whether treatment with 4 ppm of flavophospholipol is aiding in reducing Salmonella and promoting favorable indigenous bacteria in the pig microbiota as previous literature has suggested.
Date: 2020-05
Rights: Attribution-NonCommercial-NoDerivatives 4.0 International
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Attribution-NonCommercial-NoDerivatives 4.0 International Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivatives 4.0 International