Factors affecting intestinal colonisation of poultry by campylobacter and role of microflora in control

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Abstract
Although thermophilic campylobacters have sometimes caused disease in poultry, both in challenge studies and under field conditions, the organisms are usually carried asymptomatically in the alimentary tract of infected individuals. There is, however, a significant association between campylobacters in poultry and human enteritis. Properties of Campylobacter jejuni that are associated with intestinal colonisation in the bird are discussed. The organism is morphologically and physiologically well adapted to its ecological niche in the mucus-filled crypts of villi, but establishment and maintenance of colonisation involve a complex interaction between bacterium and host that has yet to be fully elucidated. Bacterial factors include the possession of intact, functional flagella and the type of flagellin expressed. Also, colonisation has been shown to depend on the expression of certain stress-response and virulence genes. Attempts to prevent or reduce campylobacter colonisation by establishing a competitive or antagonistic microflora in chicks have not always been successful, and possible reasons are considered. Some protection was obtained with bacteria such as mucin-utilising coliforms, but the protective potential of these organisms appears to be limited. In other studies, the natural occurrence of colonisation resistance has been demonstrated in broilers and its development followed. Experience suggests that the phenomenon depends on the presence of strictly anaerobic bacteria that have yet to be isolated and identified.