UBC Theses and Dissertations
The effects of meat juice on biofilm formation of Campylobacter and Salmonella Li, Jiaqi
Campylobacter and Salmonella are leading causes of foodborne illnesses worldwide. Raw meat is the common food reservoir for Campylobacter and Salmonella. Both microbes are prevalent in the meat processing environment in the form of biofilms that contribute to cross-contamination and food poisoning. This thesis project applied raw meat juice (chicken juice and pork juice) as a minimally processed food model to study its effect on bacterial biofilm formation. Meat juice was collected during raw meat freeze-thaw process and sterilized by filtration. All biofilms were developed on solid-liquid interface. Biofilm formation level was determined by live cell staining, which is based upon the metabolic activity of bacterial cells. In polystyrene 96-well plates, over 25% (v/v) of meat juice supplemented in Müeller Hinton broth could significantly (P < 0.05) enhance the survival of Campylobacter in its biofilm. Luria-Bertani broth supplemented with 10% meat juice (v/v) could lead to a significant difference (P < 0.05) in Salmonella biofilm formation compared to that without meat juice supplementation. During the initial attachment stage of biofilm development, more bacterial cells were present on the substrate with meat juice residues compared to clean substrate alone. Meat juice particles on substrates supported biofilm formation of Campylobacter and Salmonella under both static condition and flow condition achieved in a microfluidic platform. Inverted fluorescence microscope was used to determine the thickness and 3-dimensional structure of biofilms in a microfluidic chamber. Further, the deficiency in biofilm formation by selective Campylobacter and Salmonella mutant strains could be recovered in the presence of meat juice particles. Meat juice residues on the substrate may act as the conditioning layer to support initial attachment and biofilm formation of Campylobacter and Salmonella. In conclusion, these results suggest a possible survival mechanism of Campylobacter and Salmonella in the meat processing environment. In application, thorough cleaning of meat residues during meat production and handling is considered to be critical in reducing the bacterial load of Campylobacter and Salmonella.
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