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

点击翻译按钮获取中文摘要

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.