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The impact of diet, gut microbiota and environmental factors on growth and pathogenicity of Listeria monocytogenes
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Date
2025
Authors
Cazzaniga, Monica
Journal Title
Journal ISSN
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Publisher
University College Cork
Published Version
Abstract
This thesis explores how diet, gut microbiota, and host immunity interact to influence Listeria monocytogenes infection. L. monocytogenes causes listeriosis, a serious foodborne disease increasingly linked to ready-to-eat foods. While its survival in food environments is well studied, its behaviour in the gastrointestinal tract and interactions with the microbiota remain less understood. Focusing on dietary polysaccharides chitin and chitosan, we investigated their effects on Listeria virulence and host–microbiota dynamics using in vitro, in vivo, and ex vivo models. Chitin and chitosan downregulated the virulence gene hlyA and reduced bacterial adhesion and invasion, likely via the VirSR regulatory system. In mice, chitosan improved microbiota composition and metabolic outcomes under a high-fat diet but did not prevent systemic infection. Conversely, chitin reduced bacterial burden and enhanced early immune activation, suggesting dual actions on pathogen virulence and host defences. Microbiota composition strongly influenced infection outcomes: experiments in SPF and Oligo-MM12 mice, supported by ex vivo fermentation, highlighted that host factors are essential for microbiota–pathogen interactions. Unexpectedly, certain Listeria strains displayed dendritic motility at 37°C under specific nutrient conditions, revealing a novel, strain-dependent motility phenotype linked to quorum sensing.
Overall, this work shows that L. monocytogenes is highly responsive to dietary, environmental and microbial cues. These findings emphasize the potential of microbiota-informed dietary strategies for preventing foodborne infections and improving gut health.
Description
Keywords
Listeria monocytogenes , Pathogenicity , Environmental factors , Dietary compounds , Gut microbiome , Host responses , Immune responses
Citation
Cazzaniga, M. 2025. The impact of diet, gut microbiota and environmental factors on growth and pathogenicity of Listeria monocytogenes. PhD Thesis, University College Cork.