Honors Theses


Yvonne Sun



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Honors Thesis


Listeria monocytogenes is a gram-positive facultative anaerobe and harmful pathogen transmitted through contaminated food. Listeriosis, the infection associated with L. monocytogenes, is rare but potentially fatal, with a twenty to thirty percent mortality rate. For that reason, the lack of safe strategies to prevent infections can be detrimental to public health. Current infection preventative strategies rely on stringent food surveillance and recalls, but we want to determine alternative tactics to further protect the public from L. monocytogenes. More specifically, we want to identify environmental factors that can compromise the ability of L. monocytogenes to cause infections before the pathogen reaches the intestines. For example, propionate is generally recognized as safe by the FDA and is used as an additive in various food products. Alongside being a food additive, propionate is a gut metabolite found in our intestinal tract. In past studies, our lab has demonstrated that propionate exposure in L. monocytogenes can lead to changes in growth and pathogenesis. To determine how propionate exposure affects L. monocytogenes survival and fitness in the gastrointestinal tract, my thesis project therefore studies the effects of propionate on L. monocytogenes resistance to the lysozyme found in our saliva. If propionate enhances L. monocytogenes lysozyme resistance, the use of propionate in food products might contribute to L. monocytogenes survival during transmission between food and our gastrointestinal tract. However, if propionate decreases L. monocytogenes resistance to lysozyme, it could be beneficial to use propionate as an efficient infection preventative strategy. To better understand the functions of propionate in L. monocytogenes lysozyme resistance, I performed several trials of a lysozyme growth experiment and lysozyme survival assay.

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Undergraduate research