CamChain - Campylobacter in chicken production: survival, virulence and control

弯曲杆菌是欧盟一种主要的食源性病原体，估计感染1%的人。EFSA估计高达80%的病例是禽类造成的。鸡尸污染带来了两个威胁。表面水平可能很高，构成了交叉污染的风险，肠道外扩散到肌肉和肝脏增加了弯曲杆菌在烹饪中存活的机会。肉鸡在生产过程中会受到来自环境的感染。弯曲杆菌在农场和加工环境中生存、传播给肉鸡并随后定居的机制尚不清楚。我们试图确定这些过程在分子水平上发生的机制，并检查农场环境和食物链中的生存情况。对弯曲杆菌进入肉鸡舍的机制和时间以及对鸡群的初始定植缺乏了解。同样，我们对弯曲杆菌在鸡群内的流行病学了解也很差。我们将解决这些问题。鸟类的一般情况和肠道健康在弯曲杆菌的易感性中起主要作用，我们将对此进行调查。我们拟议的实地研究还将确定农场和周围环境中存在哪些弯曲杆菌菌株，这些菌株如何随时间和季节变化，以及这些菌株与这些农场肉鸡中的菌株有何关系。可以从鸡的可食用组织中分离到弯曲杆菌。研究表明，宿主应激和先天免疫反应可以产生侵袭性的弯曲杆菌表型。关于弯曲杆菌离开鸡肠的机制，我们一无所知。我们将使用后基因组技术确定这些以及肠道定植的机制。我们将研究通过使用潜在的益生菌和益生菌饲料来提高鸟类对弯曲杆菌的抵抗力的方法。过去的工作取得了好坏参半的结果，但我们的初步数据表明，我们有潜力的产品。我们将确定它们对弯曲杆菌携带、鸟类肠道健康和肠道微生物群的影响。两者都在鸟类对弯曲杆菌的易感性中发挥作用，并影响其在体内的行为。我们将根据鸡群弯曲杆菌阳性还是阴性、集群定植水平以及盲肠和身体上的细菌数量来衡量成功与否。目前尚不清楚弯曲杆菌如何在“恶劣条件”中生存，也不清楚这种暴露是否会影响其毒力。弯曲杆菌被认为是脆弱的，但在农场和鸡尸上却能很好地存活。体外研究表明，与其他微生物共培养的空肠弯曲菌能更好地在不利条件下生存。微生物群落在自然和农场环境中共存的弯曲杆菌生态中的作用尚未被研究。我们将确定弯曲杆菌的水平和农场环境中存在的不同菌株，以及它们如何受到气候、天气和季节的影响。对弯曲杆菌在农场和加工环境中对压力的分子反应缺乏了解。过去的工作表明，空肠弯曲菌分离株在恶劣环境中的生存能力不同。其他工作发现，分离株的毒力不同。还没有做的是在分子水平上确定环境弹性、应激反应和毒力之间是否存在关系。这是拟议工作的一个重要目标，也是有效控制食物链中病原体的目标之一。

Campylobacter is a major food borne pathogen in the EU, estimated to infect 1% of people. EFSA estimates that poultry is responsible for up to 80% of cases. Chicken carcass contamination presents two threats. Surface levels can be high, posing a cross-contamination risk and extra-intestinal spread to muscle and liver increases the chance that Campylobacter survives cooking. Broilers become infected during production from the environment. Mechanisms by which Campylobacter survives in the farm and processing environments, transmits to broilers and subsequently colonises them are not well understood. We seek to identify the mechanisms by which these processes occur at the molecular level and examine survival in the farm environment and through the food chain. Understanding of the mechanism and timing of entry of Campylobacter into broiler houses and initial colonisation of the flock is lacking. Similarly, our understanding of the within flock epidemiology of Campylobacter is poor. We will address these issues. Bird general and gut health play major roles in susceptibility to Campylobacter and we will investigate this. Our proposed field studies will also determine what strains of Campylobacter are present in the farm and surrounding environment, how these vary over time and by season and how such strains relate to those in broilers on those farms. Campylobacter can be isolated from edible tissues of chickens. Research suggests that host stress and innate immune responses can create invasive Campylobacter phenotypes. Nothing is known about mechanisms by which Campylobacter leaves the chicken gut. We will identify these and the mechanisms for intestinal colonisation, using post-genomic techniques. We will examine methods for enhancing bird resistance to Campylobacter through the use of potentially probiotic bacteria and prebiotic diets. Past work has had mixed success but our preliminary data indicate that we have products with potential. We will determine their effects on Campylobacter carriage, bird gut health and the gut microbiome. Both play a role in susceptibility of birds to Campylobacter and also influence its in vivo behaviour. We will measure success on the basis of whether flocks are Campylobacter-positive or -negative, on levels of flock colonisation and numbers of the bacteria in caeca and on carcasses. It is not well known how Campylobacter survives in 'hostile conditions' or whether such exposure affects virulence. Campylobacter is considered to be fragile yet survives well on farm and on chicken carcasses. In vitro studies show that C. jejuni co-cultured with other microbes can better survive adverse conditions. The role of microbial communities in Campylobacter ecology that co-occur in natural and farm environments has not been studied. We will determine levels of Campylobacter and the different strains present in farm environments and how they are affected by climate, weather and season. There is a lack of understanding of the molecular response of Campylobacter to stresses in the farm and processing environments. Past work showed that C. jejuni isolates differ in survival in hostile environments.Other work found that isolates differ in virulence. What has not been done is to establish whether there is a relationship between environmental resilience, stress responses and virulence at the molecular level. This is an important objective of the proposed work and one which leads to effective control of the pathogen in the food chain.