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

受病原体污染的食物的危害在许多加拿大人的脑海中是新鲜的，并且源于最近与E。大肠杆菌O 157：H7污染的牛肉产品遍布北美。相应地，食品安全失败的后果是相当感兴趣的加拿大人。关于单核细胞增生李斯特菌，估计99%的李斯特菌病病例来自受污染的食物。因此，需要改进旨在更有效地控制Lm的缓解策略，以减少召回率和结核病发生率。为此，我的研究计划旨在确定有助于食物链生存的因素，使更有效的Lm缓解。目前，我们正在关注最近在熟食和BC海鲜中发现的基因组岛（LGI 1）。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，携带LGI 1的菌株最近被证明形成了一种新的流行性克隆（ECV），自1988年以来在加拿大引起了人类疾病。为了阐明LGI 1基因是否有助于食物链生存和/或毒力，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LGI 1的Lm 1/2a血清型菌株与具有LGI 1的1/2a菌株，以观察耐受食物相关应激（酸性pH值，高盐）和消毒剂的能力是否存在差异。类似地，我们将确定具有LGI 1的Lm是否更有效地粘附于食物表面和肠上皮细胞。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LGI 1的贡献。同样，由于LGI 1编码一个交替的sigma因子和一个双组分调节因子，因此将采用RNA测序来研究编码LGI 1的菌株中可能的应激反应/调节差异。这项研究计划将为LGI 1的作用提供新的知识。考虑到其与加拿大临床肺结核的相关性，这种认识是至关重要的，并将为制定新的和/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.