Leah Allen, Stephanie Johnson



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The human gut microbiome is recognized as an important contributor to human health. The functional roles of the gut microbiome are under active investigation to increase our knowledge in human biology and develop novel therapeutics. For example, gut microbes produce short chain fatty acids (SCFAs), which have demonstrated regulatory and nutritional functions in the intestines and peripheral organs. However, how SCFAs contribute to defense against infectious diseases is less understood. Therefore, the overarching goal of our research is to determine the roles of SCFAs during host-pathogen interactions. More specifically, we are investigating how exposure to propionate, a key SCFA found in humans, affects the outcome of Listeria monocytogenes infections in macrophages. L. monocytogenes is an opportunistic pathogen transmitted through contaminated food. In high risk individuals, infections may become life-threatening. One unique aspect of L. monocytogenes that allows the bacterium to act as a human pathogen is its ability to grow inside macrophages without elimination by the antimicrobial arsenal deployed by the macrophages. Therefore, strategies that can compromise the bacterial intracellular growth or strengthen the antimicrobial capacity of macrophages can potentially protect individuals from L. monocytogenes infections. In this study, we investigated how propionate affects nitric oxide production, phagocytic activity, and elimination of intracellular L. monocytogenes in a cell culture model of infection. We found that propionate-treated macrophages, compared to non-treated controls, exhibited a significantly higher phagocytic activity. Moreover, activated macrophages produced decreasing levels of nitric oxide after exposure to increasing levels of propionate. Finally, the presence of propionate during infection resulted in a significantly lower intracellular bacterial numbers. Together, these results suggest that the presence of propionate can alter macrophage functions that lead to restriction of L. monocytogenes intracellular growth, an observation that will need to be further investigated to develop strategies to protect individuals from L. monocytogenes infections.

Publication Date


Project Designation

Independent Research

Primary Advisor

Yvonne Y. Sun

Primary Advisor's Department



Stander Symposium project, College of Arts and Sciences

United Nations Sustainable Development Goals

Good Health and Well-Being

The Role of Propionate During the Interactions Between Macrophages and Listeria monocytogenes