Date of Graduation

12-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

Young Ming Kwon

Committee Member

Billy M. Hargis

Second Committee Member

Steven C. Ricke

Third Committee Member

Ravi Barabote

Keywords

Barcode-tagged isogenic strain, chicken, probiotics, salmonella, salmonella transmission, vaccine

Abstract

Salmonella is a major foodborne pathogen around the world and chickens are the major reservoir to transmit Salmonella into the human food chain. For decreasing the infection of Salmonella, we developed six attenuated live vaccines based on Salmonella Enteritidis (SE) and Typhimurium (ST) for testing the cross-serovar and cross-serogroup protection from the challenge of Salmonella Heidelberg and Campylobacter jejuni. One of the constructed vaccine strain showed ability to protect against challenge from Salmonella Heidelberg. Even though some preventive approaches are able to decrease Salmonella colonization in the gastrointestinal tract of chickens or other farm animals, Salmonella transmission mechanisms remain unclear. For analyzing Salmonella transmission routes and dynamics, we designed a series of Salmonella isogenic barcode-tagged strains by inserting six random nucleotides into a functionally neutral region on the chromosome of Salmonella Enteritidis. These barcode-tagged strains can be used as a tool for quantitative tracking of Salmonella transmission in the chicken flock by profiling the barcode regions using high-throughput sequencing. The efficiency of this novel approach has been estimated by chicken experiments and can be applied for further studies about Salmonella transmission and population dynamics. Due to the increasing pressure of using antibiotics as the growth promoter in the farm animals, probiotics is a suitable alternative to replace antibiotics by providing beneficial effects, such as promotion of animal health, decreased infection by pathogens, and improval of growth performance in poultry. In this study, 90 probiotic candidate strains were isolated and evaluated for decreasing the gut permeability in Caco-2 cell lines. The result from animal experiments indicated that a combined batch culture of 3 selected strains showed significant efficacy in controlling intestinal colonization of ST in neonatal turkey poults.

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