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Brenner, Thomas

University of British Columbia

Poultry products are the largest food category linked to foodborne salmonellosis. A small subset of serovars within the subspecies Salmonella enterica are the most prevalent sources of human disease, causing a substantial burden of illness in Canada. Barriers along the poultry production continuum favour the survival of these serovars due to niche-specific genes which encode resistance to selective pressures such as host defenses and industrial antimicrobial practices. Bacteriophages (phages) have been proposed as novel antimicrobials in the poultry industry due to their documented safety, ubiquity, and unparalleled target specificity. This research explores the usefulness of environmentally isolated phages, for application in free and encapsulated forms, to target prominent poultry-associated S. enterica serovars in Canada. Fifty S. enterica isolates, representing seven pervasive serovars, were procured by the British Columbia Ministry of Agriculture from environmental and diagnostic poultry sources. The quantity and diversity of antimicrobial resistance (AMR) genes, virulence factors, Salmonella Pathogenicity Islands, and plasmids, across our S. enterica library, were identified for each bacterial isolate using whole genome sequences. Serovar-specific differences were identified that likely play a role in the recent shift in Salmonella serovars across the Canadian poultry sector. AMR profiles were confirmed in vitro by minimum inhibitory concentration testing. A library of 78 phages, isolated from environments in British Columbia, Canada, was evaluated against S. enterica strains. Host range testing followed by relative host efficiency narrowed down candidates to six best phages for cocktail formulation. Promising phages were characterized using one-step growth curves and transmission electron microscopy. A broad-spectrum cocktail containing three phages was successfully produced with high killing efficacy across all 50 poultry-associated S. enterica isolates in vitro. This cocktail produced a 3.21 log reduction when sprayed directly onto chicken breast challenged with a mixture of S. enterica serovars. Phage cocktail protected in a microemulsion and ingested by mature broiler chickens, resulted in a 1.50 log Salmonella reduction in birds challenged with a mixture of S. enterica serovars. Lastly, 16S rRNA gene sequencing indicated that the upper, middle, and lower gastrointestinal tract of broilers had negligible differences in microbiome composition across phage treatment groups.

Text

2024-01-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83629

Food Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/