Identification and characterization of novel genetic factors contributing to the significance of Listeria monocytogenes as a foodborne pathogen

受病原体污染的食品的危险在许多加拿大人的脑海中历历在目，源于最近爆发的与受大肠杆菌O157：H7污染的牛肉产品在北美广泛分布有关的疫情。相应地，加拿大人对食品安全失误的后果非常感兴趣。关于单核细胞增多性李斯特菌，估计99%的李斯特菌病病例来自受污染的食物。因此，需要改进缓解策略，以更有效地控制LM，以减少召回和李斯特菌病的发生率。为此，我的研究计划旨在确定有助于食物链存活的因素，使之能够更有效地缓解LM。目前，我们关注的是最近在熟食店肉类和不列颠哥伦比亚省海鲜中发现的基因组岛(LGI1)。该胰岛编码可能的胁迫反应、季铵盐化合物抗性和毒力基因。值得注意的是，携带LGI1的菌株最近被证明形成了一种新的流行病克隆(ECV)，并自1988年以来在加拿大引起了人类疾病。为了阐明LGI1基因是否有助于食物链存活和/或毒力，我的研究计划将使用传统和分子方法来解决假说。简而言之，我们将比较缺乏LGI1的LM1/2a血清型菌株和具有LGI1的1/2a菌株，看看在耐受与食物相关的压力(酸性pH，高盐)和消毒剂方面是否存在差异。同样，我们将确定是否有LGI1的LM更有效地附着在食物表面和肠道细胞上。为了补充这些传统的食品微生物学方法，我的计划还将使用qPCR和有针对性的基因缺失/互补来确认LGI1的贡献。此外，由于LGI1编码一个替代的sigma因子和一个双组分调节因子，因此将使用RNA测序来研究编码LGI1的菌株之间可能的应激反应/调节差异。这项研究计划将对LGI1的作用提供新的知识。考虑到它与加拿大临床李斯特菌病的关联，这种洞察力是至关重要的，并将为新的和/或改进的控制策略提供基础。

The perils of pathogen-contaminated food are fresh in the minds of many Canadians, and stem from the recent outbreak linked to widespread distribution of E. coli O157:H7 contaminated beef products across North America. Correspondingly, consequences of food safety failures are of considerable interest to Canadians. Regarding Listeria monocytogenes (Lm), 99% of listeriosis cases are estimated to derive from contaminated food. Therefore, improved mitigation strategies aimed at more effective control of Lm are required to reduce recalls and rates of listeriosis. To this end, my research program aims to identify factors contributing to food chain survival that enable more effective Lm mitigation. At this time, we are focusing on a recently discovered genomic island (LGI1) reported in deli meat and BC seafood. This islet encodes putative stress response, quaternary ammonium compound resistance, and virulence genes. Notably, strains carrying LGI1 were recently shown to form a new epidemic clone (ECV), and have caused human disease in Canada since 1988. To elucidate whether LGI1 genes contribute to food chain survival and/or virulence, my research program will use traditional and molecular approaches to address hypotheses. In short, we will compare Lm 1/2a serotype strains lacking LGI1 to 1/2a strains possessing LGI1 to see if differences exist in the ability to tolerate food-related stress (acidic pH, high salt) and sanitizers. Similarly, we will determine if Lm having LGI1 adhere to food surfaces and enterocytes more effectively. To complement these traditional food microbiology approaches, my program will also use qPCR and targeted gene deletion/complementation to confirm LGI1 contributions. As well, since LGI1 encodes an alternate sigma factor and a two-component regulator, RNA sequencing will be employed to investigate possible stress response/regulatory differences in strains encoding LGI1. This research program will contribute new knowledge regarding the role of LGI1. Considering its association with clinical listeriosis in Canada, such insight is critical, and will provide a foundation from which new and/or improved control strategies will evolve.