SubPopulations of Shiga Toxin Producing Escherichia coli: Persistence, Resistance and Pathogenicity

实验微生物学通常假设细菌种群在抗应激或基因表达方面是同质的。然而，在现实中，纯菌株培养物是异质的，其中一部分细胞处于休眠（持久）状态，与群体的主体相比具有增强的抗性。此外，休眠细胞在培养过程中会被遗漏，因为它们要么失败，要么生长延迟。从进化的角度来看，这种持续状态是一种“赌注对冲”，如果种群的条件变得不利，一定比例的细胞将在较长时间内存活下来。迄今为止，大多数与持久性有关的研究都是关于抗生素治疗后剩余的残留种群。然而，持久性通常在更广泛的环境中遇到，如土壤和食品系统，如高压加工处理的食品。尽管病原体再生长或毒性增强的可能性都是可能的，但残留种群对食品安全的重要性尚不清楚。在拟议的研究计划中，我们将研究产滋贺毒素的大肠杆菌（STEC）的休眠（持续、VBNC和耐受）状态，这是一类重要的临床和食源性病原体。这是第一次，持久状态将在 *STEC中进行研究，并确定引发或打破休眠状态的触发因素。与此相关的是来自土壤微生物群 * 和根际的持久性调节剂，它们最终控制病原体：植物相互作用。这将是 * 第一次，它将证明如何影响噬菌体和宿主的相互长期生存的持久状态 *。对持续状态的研究将使用最先进的成像技术与微流体技术相结合，从而能够在单细胞水平上进行操作/观察。将产生和收获处于持久状态的细胞，以便于研究休眠在抗高压和溶解性破坏中的作用，以及环境持久性。这项研究的影响可能是广泛的。从学术的角度来看，* 更深入的了解原噬菌体宿主的相互作用将获得。在应用方面，这项研究将提供数据，以评估环境和食品系统中持久性细胞所代表的食品安全风险。到目前为止，风险分析经常指定一个特定的对数减少值来验证干预措施（例如巴氏灭菌）的有效性，而不考虑剩余的幸存者。虽然存在于低水平，残留的幸存者可以在储存过程中增长或在宿主体内变得更具毒性。这项研究将提供数据来评估这种风险，并通过打破休眠状态来制定更有效的病原体控制策略。

Experimental*microbiology typically assumes bacterial populations are homogenous with*respect to resistance to stress or gene expression. However, in reality pure*strain cultures are heterogeneous with a proportion of cells existing in a*dormant (persistent) state that have enhanced resistance compared to the main*body of the population. Moreover, dormant cells are missed during culturing as*they either fail or experience delayed growth. In evolutionary terms the*persistent state is a kind of “bet hedging” whereby a proportion of cells will*survive over extended periods should conditions for the population become*adverse. To date, the majority of studies relating to persistence has been with*respect to residual populations remaining after antibiotic treatment. Yet,*persistence is commonly encountered in the wider environment such as soil, and*food systems, such as foods treated with high pressure processing. The*significance of residual populations with respect to food safety is unknown*although the potential for the re-growth of pathogens or enhanced virulence are*both possibilities. In the proposed research program we will look at the*dormant (persistent, VBNC and tolerant) state in Shiga Toxin producing*Escherichia coli (STEC) a class of significant clinical and foodborne*pathogens. For the first time, the persistent state will be investigated in*STEC and the triggers that both induce or break the dormant state identified.*Of relevance will be the regulators of persistence derived from soil microbiota*and rhizosphere that ultimately control pathogen:plant interactions. For the*first time, it will be demonstrated how prophage influences the persistent state*leading to mutual long term survival of phage and host. Studies of the*persistent state will use state-of-the-art imaging techniques in*combination with microfluidics that enable manipulation/ observation at the*single cell level. Cells in the persistent state will be generated and*harvested to facilitate studies on the role of dormancy in resistance to high*pressure and lytic phages, in addition to environmental persistence. The impact*of the research is potentially wide reaching. From an academic standpoint*greater insights into prophage host interactions will be obtained. On an*application side the research will provide data to assess the food safety risks*represented by persister cells in the environment and food systems. To date,*risk analysis has frequently designated a specified log reduction to verify the*efficacy of interventions (for example, pasteurization) without taking into*account residual survivors. Although present at low levels, residual survivors could grow during storage or become more virulent within the host. The research will provide data to*assess such risks and moreover lead to more effective pathogen control*strategies through breaking of the dormant state.******