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对许多加拿大人来说是新鲜的，这源于最近与北美地区广泛分布的受大肠杆菌O157:H7污染的牛肉产品有关的疫情。相应地，食品安全失败的后果是加拿大人相当感兴趣的。关于单核细胞增生李斯特菌（Lm），估计99%的李斯特菌病病例来自受污染的食物。因此，需要改进缓解战略，以更有效地控制李斯特菌病，以减少召回和李斯特菌病发病率。为此，我的研究计划旨在确定有助于食物链生存的因素，从而能够更有效地缓解Lm。目前，我们正在关注最近在熟食肉和BC海鲜中发现的基因组岛（LGI1）。该胰岛编码推定的应激反应、季铵化合物抗性和毒力基因。值得注意的是，最近显示携带LGI1的菌株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基因是否对食物链生存和/或毒性有贡献，我的研究计划将使用传统和分子方法来解决假设。简而言之，我们将比较缺乏LGI1的Lm 1/2a血清型菌株与具有LGI1的1/2a菌株，以了解在耐受食物相关应激（酸性pH，高盐）和消毒剂的能力方面是否存在差异。同样，我们将确定LGI1是否更有效地粘附在食物表面和肠细胞上。为了补充这些传统的食品微生物学方法，我的项目还将使用qPCR和靶向基因缺失/互补来确认LGI1的贡献。此外，由于LGI1编码一个备用sigma因子和一个双组分调节因子，RNA测序将用于研究编码LGI1的菌株可能的应激反应/调节差异。该研究项目将对LGI1的作用提供新的认识。考虑到它与加拿大临床李斯特菌病的关联，这种见解至关重要，并将为新的和/或改进的控制策略的发展提供基础。

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.