Investigating mechanisms of gallbladder persistence in Salmonella

This project endeavours to understand how the S.Dublin Salmonella serovar is able to persist after symptomatic infection in the bovine gallbladder. Cattle are reservoirs of S.Dublin which can cause typhoidal symptoms in cows, leading to high calf mortality and abortions in infected mothers. Not only does this affect the productivity of the dairy industry, but S.Dublin can be zoonotically transferred to humans where it can also cause typhoidal disease. As an emerging One Health problem due to its high mortality in cattle and humans, understanding the mechanisms of Salmonella persistence can help to improve animal health and prevent the transfer of S.Dublin to humans.
By creating a transposon mutant library and passaging S.Dublin through different media, including concentrated bile to recreate the conditions of the gallbladder, we can determine what genes might play a role in Salmonella persistence. This will be done by using transposon-directed insertion-site sequencing (TraDIS) to identify which genes are overexpressed and under-expressed in conditions replicating the gallbladder. From there genes of interest can be determined and then further experiments can be used to understand how the mediate persistence. It is proposed that changes in motility, invasion, biofilm formation and antimicrobial resistance will be investigated by changing the environmental S.Dublin culture conditions to ascertain the methods of bacterial persistence.
To reduce the use of animals the project, ex vivo gallbladder models will be developed to passage S.Dublin to determine the levels of gene expression of genes of interest. The 3Rs is an important target for sustainable research and it is exciting that this project actively aims to produce a viable model that can be utilised by multiple research groups to avoid animal use. Gallbladder organoids could also be used to understand how S.Dublin interacts with epithelial and immune cells and, as a stretch goal for the project, genetic manipulation could be used to understand if host genes contribute to Salmonella persistence.