Understanding the Effects of Propionic Acid on Listeria monocytogenes Growth, Survival, and Virulence.
Elizabeth A Abrams, Kaitlin E Beemiller, Eric Edward Newton, Erica Rinehart, Nathan C Wallace
Listeria monocytogenes is a bacterial pathogen that causes foodborne gastrointestinal illnesses. In the absence of a strong immune system, Listeria can cause fatal infection by breaking the intestinal wall and spreading to other organs. Therefore, prevention of fatal infections relies on blocking Listeria from adhering to the intestinal wall. My work focused on understanding how propionate, a natural intestinal acid in healthy individuals, affects Listeria’s ability to grow and cause disease. We first conducted growth curves in BHI and found that propionate supplementations with concentrations up to 25mM resulted in a small decrease in in vitro growth under both aerobic and anaerobic conditions. In contrast, using hemolytic assays, we found that propionate supplementation resulted in a significant increase in listeriolysin O (LLO) supernatant activity after anaerobic growth, but a significant decrease in LLO supernatant activity after aerobic growth. To further determine the effect of propionate on Listeria pathogenesis, we infected RAW264.7 macrophages with Listeria grown aerobically or anaerobically, with or without propionate supplementations. Our results showed that compared to aerobically grown Listeria, anaerobically grown Listeria exhibited significantly higher intracellular CFUs during early infection time points, but lower intracellular CFUs during later time points. Supplementation of propionate during Listeria in vitro growth did not impact intracellular growth. Finally, we tested the hemolytic ability and intracellular growth of environmental Listeria isolates and saw results mimicking those of our lab strain. Together, our results suggest that Listeria is capable of growth with high levels of propionate but likely adapts to propionate differently depending on the presence or absence of oxygen. Further research is being conducted to test for protective effects of propionate on mammalian cells by treating the cells with propionate prior to infection. We hope to fully understand the extent of influence propionate has on host-pathogen interactions.
Honors Thesis - Graduate
Primary Advisor's Department
Stander Symposium project
"Understanding the Effects of Propionic Acid on Listeria monocytogenes Growth, Survival, and Virulence." (2017). Stander Symposium Projects. 1069.