Host acute stress responses and the regulation of C. jejuni virulence in the avian gut

食品生产商努力将消费者食物中毒的风险降至最低。感染人类的最重要的食物相关细菌是弯曲杆菌，它天然存在于大量生家禽产品中。如果弯曲杆菌可以从农场的鸡中消除，它将对人类健康产生重大影响，每年防止数千起食物中毒事件。如果要实现控制，我们必须更好地了解弯曲杆菌如何感染鸡，动物宿主和病原体如何相互作用，以及现代生产方法对这种相互作用的影响。环境和耕作方法都会影响农场的微生物学。现代养鸡业是高度集约化的，即使有访客在场也会给动物造成压力。我们的假设是，鸡的压力水平增加可能导致弯曲杆菌在鸟类中的水平升高，并导致细菌的行为与正常情况非常不同。其原因尚不清楚，但可能涉及肠道中保护性细菌数量的变化，免疫力的改变以及病原体适应性的增加，从而损害了动物抵抗感染的能力。动物受到压力或疼痛时会在全身释放神经递质。例如，一只被抓到并被运到屠宰场的应激鸡的肠道中会有更高水平的神经递质。这方面的主要神经递质是去甲肾上腺素，其水平在压力期间会迅速增加。去甲肾上腺素会通过改变肠道细胞的渗透性和改变体液平衡来影响动物，但它也会改变肠道中病原菌的性质和行为。例如，布里斯托大学最近的研究表明，弯曲杆菌在去甲肾上腺素的存在下生长得更快，运动性更强。沙门氏菌和E.大肠杆菌的研究表明，细菌细胞表面结构，在动物感染中很重要，也受到去甲肾上腺素的影响。这项工作的目的是了解去甲肾上腺素对弯曲杆菌的影响，特别是细菌如何获得铁，与动物组织相互作用，以及这如何影响对感染重要的基因的表达。这项工作将探索去甲肾上腺素允许弯曲杆菌从肠道转移到其他组织的假设，它也使细菌能够更好地在农场环境中生存。更好地了解弯曲杆菌与应激宿主之间的相互作用最终可以提高动物福利并提高食品安全。

Food producers strive to minimise the risks of food poisoning for consumers. The most important food-associated bacterium, which infects humans, is Campylobacter, which is naturally present in large numbers of raw poultry products. If Campylobacter could be eliminated from chickens on the farm it would have a significant impact on human health by preventing many thousands of cases of food poisoning each year. If control is to be achieved it is important that we better understand how Campylobacter infects chickens, how the animal host and the pathogen interact, and the impact that modern production methods have on this interaction. Environment and farming practices all influence the microbiology of the farm. Modern chicken production is highly intensive and even the presence of a visitor can cause stress to the animals. Our hypothesis is that increased levels of stress in chickens may lead to higher levels of Campylobacter in the birds and cause the bacterium to behave in a very different way from normal. The reasons for this are not clear, but may involve changes in the populations of protective bacteria in the gut, alterations in immunity, and increased pathogen fitness compromising the animal's ability to resist infection. Animals stressed or in pain release neurotransmitters throughout their body. For example, a stressed chicken being caught and transported to the slaughterhouse will have higher levels of neurotransmitters in its gut. The main neurotransmitter in this respect is noradrenaline and levels of this can increase rapidly during stress. Noradrenaline will affect the animal by altering the permeability of the gut cells and by changing fluid balance, but it will also change the nature and behaviour of pathogenic bacteria in the gut. For example, recent work at the University of Bristol has shown that Campylobacter grow much more quickly and are more motile in the presence of noradrenaline. Other research on Salmonella and E. coli showed that bacterial cell surface structures, important in animal infection, are also influenced by noradrenaline. The purpose of this work is to understand the effects of noradrenaline on Campylobacter, particularly on how the bacterium acquires iron, interacts with animal tissues, and how this affects the expression of genes important for infection. The work will explore the hypothesis that noradrenaline allows translocation of Campylobacter from the gut to other tissue and that it also makes the bacteria better able to survive in the farm environment. A better understanding of the interaction between Campylobacter and the stressed host could eventually enhance animal welfare and improve food safety.