Transcription Regulation of Salmonella enterica serovar Typhimurium Adaptation to Food Matrices, Protozoan Host, and Oxidative Stress

Abstract

Salmonella poses a significant threat to public health, especially in poultry. As a facultative intracellular pathogen, it survives within macrophages and protozoa by utilizing horizontally acquired pathogenicity islands such as SPI-1, which facilitates invasion, and SPI-2, which supports intracellular survival. Protozoa such as Acanthamoeba castellanii can harbor Salmonella, providing a protected reservoir that may enhance its environmental persistence. We hypothesize that, similar to macrophages, Salmonella employs DNA-binding transcription factors (TFs) to adapt and proliferate within amoebae by regulating gene expression. This thesis explores how transcription factors help Salmonella adapt to intra-amoebic conditions as well as poultry-based food matrices like egg yolk and chicken meat. It also examines the role of the SPI-2 encoded regulator Orf242 in intracellular stress responses. Deletion of TFs such as Orf242, SoxS, Fis, and Fur significantly reduced Salmonella's proliferation in egg yolk and chicken meat, whereas deletion of Orf242, SoxS, and Fur impaired its ability to survive within amoebae. Although its deletion did not significantly affect oxidative stress tolerance, further research on Orf242’s function under acidic and anaerobic stress is needed. Targeting these mechanisms may help reduce the pathogen load in environmental reservoirs and, subsequently, pre-harvest contamination in poultry production.