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

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.

We comprise groups in Europe, Thailand and Viet Nam. The Thai government will fund work there and that in Viet Nam will be funded by Wellcome Trust and the Dutch Government. Our work will address knowledge gaps on the behaviour of Campylobacter in the poultry chain. We need to better understand interactions between Campylobacter, chickens and the environment and how these affect food safety. We will create a holistic picture of Campylobacter behaviour in chicken production and fundamental data on survival, how environmental exposures affect virulence and on-farm population biology and on pre- and/or probiotic intervention on-farm to reduce Campylobacter levels entering the food chain. We will use modelling and risk assessment tools to identify and test the potential efficacy of different interventions that can be utilised by the international poultry industry. We will determine the role of flies as vectors of Campylobacter to broilers and develop improved surveillance tools in order to reduce the number of Campylobacter in broiler meat
We aim to better understand the behaviour of Campylobacter in poultry production to improve control. We will generate understanding of mechanisms for:
In-flock transmission and risk in production including bird to bird spread in-house and downstream in the production chain
Virulence encompassing both broiler colonisation and extra-intestinal spread
Interventions for improving host resistance based on enhancing gut health and, in so doing, finding points for control
Environmental survival and the impact of environmental exposures on virulence. During these processes will be deterine pathogen source and persistence mechanisms
Population evolution to examine how the production chain selects certain sub-types of Campylobacter and whether the selection processes change virulence potential

Campylobacter is the most important food borne zoonosis in the UK and the wider EU. In the UK it is estimated that there are 700000 cases of infection each year and that chicken-associated Campylobacter infection costs the UK economy ~£1 billion per year. Chicken is overwhelmingly the most important vehicle for human infection and is believed to be responsible for up to 80% of infections. ~80% of chickens on sale in the UK are Campylobacter-positive. Contaminated chicken presents two health threats. Surface contamination levels can be very high and contamination of deep muscle and liver tissues has been reported in up to 27 and 60% of samples tested respectively. The project seeks to better understand the processes that allow Campylobacter, and principally Campylobacter jejuni, to survive in the poultry production chain in the EU and in Thailand and to determine how exposure to potentially hostile environments affects virulence and bacterial population structures. We will also provide a comprehensive understanding of the molecular mechanisms used by C. jejuni to colonise the chicken gut and to leave there and infect edible tissues. We will examine the role of chicken gut health in the processes of Campylobacter infection and explore the use of pro- and prebiotics to better protect the birds from this major zoonotic pathogen.
The project is in partnership with the EU poultry industry and that in Thailand and all major UK retailers. Thus the beneficial impacts of our work can quickly be transferred to stakeholders.