The Effects of Short Chain Fatty Acids and Oxygen Levels on Listeria Monocytogenes Pathogenesis

Listeria monocytogenes is Gram positive foodborne pathogen that secreteslisteriolysin O (LLO), a pore-forming toxin to establish its intracellular life cycle insidehost cells. However, how the environment in the intestine that has both an oxygengradient (low oxygen to no oxygen) and is enriched in short chain fatty acids (SCFAs)affects L. monocytogenes virulence regulation and pathogenesis has not been determined.Thus, the main goal of my thesis research is to understand the effects of anaerobicity andSCFA mixtures on L. monocytogenes pathogenesis. Chapter I compiles and summarizes current findings on the production,mechanisms of action, and potential health benefits of the SCFA propionate. Followingthis review, Chapter II explores the effect of propionate on growth, membranecomposition, and hemolytic activity of L. monocytogenes under aerobic or anaerobic iv conditions. We further tested the effects of SCFA mixtures on the pathogenesis of twodifferent strains of L. monocytogenes (10403s and 07PF0776) in Chapter III to betterestablish the relevance of our findings. Finally, Chapter IV includes preliminary in vivoresults from a young and aged mouse model of infection to determine the effects ofSCFAs on dissemination of L. monocytogenes strains 10403s and 07PF0776 after oralinoculation. Together these findings support that L. monocytogenes responds in a straindependent manner to SCFAs and oxygen exposure and alters the outcomes of subsequentin vitro and in vivo infections