The Complex Roles of Propionate on the Interactions Between \u3cem\u3eListeria monocytogenes \u3c/em\u3eand Macrophages

Propionate is a short chain fatty acid (SCFA) produced by gut microbiota and is also present in food as an antimicrobial supplement. Propionate plays several important immunomodulatory roles and in more recent years has been considered for its potential to modulate bacterial infections. Listeria monocytogenes is a Gram-positive foodborne pathogen capable of causing severe disease. The main goal of this research is to better understand the effects of propionate on the interactions between L. monocytogenes and host through in vitro cell culture models. Chapter I summarizes the current knowledge on the production of propionate by the gut microbiota, mechanism of uptake and action, the role of propionate in the immune system, as an antimicrobial agent, and in the host-pathogen relationship. In Chapter II, we explore the effects of propionate on infection when using it as a pretreatment of L. monocytogenes pretreatment of host cells, or treatment during infection. Additionally, both aerobic and anaerobic L. monocytogenes growing conditions are considered. Finally, Chapter III explores the mechanism of how propionate treatment of L. monocytogenes influences infections by looking at stress resistance, metabolism, and the role of the alternative sigma factor, SigB. Together, these results support propionate as a critical modulator of L. monocytogenes infections with a complex regulatory mechanism. Future research will help establish more effective safety guidelines and infection prevention strategies