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Listeria monocytogenes is an infectious bacterium that is known to cause severe diseases in people who are pregnant, elderly, or generally immunocompromised through consumption of contaminated food products. To help develop preventative strategies to protect these high-risk individuals, our lab focuses on the approach of enhancing the chemical barrier naturally existing in the intestinal tract to block L. monocytogenes from interacting with the human intestinal epithelium and causing fatal infections. The chemical environment inside the human intestinal lumen is rich with fermentation acids produced by the endogenous microbes. In my research project, I tested the efficacy of propionic acid, one of the three major fermentation acids naturally abundant in the human gastrointestinal tract, against the in vitro growth of L. monocytogenes. If propionic acid exhibits inhibitory effect on L. monocytogenes growth, then it can be further developed into a preventative tool against L. monocytogenes infections. To determine the effect of propionic acid on L. monocytogenes growth, I supplemented L. monocytogenes cultures with 0, 5, 15, 25mM of sodium propionate and grew the culture either aerobically with continuous agitation for oxygen saturation or anaerobically inside an anaerobic chamber with a 2.5% hydrogen in nitrogen atmosphere. I monitored bacterial growth by measuring culture optical density every hour for 8 hours and calculated bacterial doubling time during the exponential phase of the growth. I observed that under aerobic conditions, propionate supplementations did not cause a significant impact on bacterial doubling time. However, under anaerobic conditions, propionate supplementation at 25mM led to a significantly increased doubling time, a result indicating an inhibitory effect of propionate on growth. These results demonstrate an inhibitory effect of a naturally occurring fermentation acid in the human intestines and therefore highlighted the potential values for propionic acid as a preventative chemical agent against L. monocytogenes infections.

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Independent Research

Primary Advisor

Yvonne Sun

Primary Advisor's Department



Stander Symposium poster


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