Potential use of characterised hyper-colonising strain(s) of Campylobacter jejuni to reduce circulation of environmental strains in commercial poultry.

Sixty-two persistently colonising Campylobacter jejuni strains were tested for their ability to dominate colonisation of the chicken gastrointestinal tract in competition with each other leading to selection of dominant or "hyper-colonising"Campylobacter strains, which are able to displace others in the chicken intestinal tract. One such strain was shown to be a hyper-efficient coloniser of chickens, as it was able to displace other colonising strains, as well as maintain itself in the chicken intestinal tract for the duration of the 56-day broiler production cycle. Once colonisation was established, this hyper-colonising C. jejuni strain, 331, could not be displaced by other colonising or hyper-colonising strains. We proposed that a defined, hyper-colonising strain, or a cocktail of defined strains with a similar phenotype, could form the basis for biological control of unknown/uncharacterised Campylobacter strains from the environment that continuously colonise chicken flocks. To validate this approach, three different chicken infection trials were carried out. These trials demonstrated that the dominant strain of C. jejuni was able to colonise broiler chickens consistently and for the entire life of the birds irrespective of the day of inoculation and antimicrobial agents used in the feed to control other pathogenic micro-organisms. In addition, we have shown that the bio-control strain was able to replace other colonising strains at various points of a 56-day broiler production cycle irrespective of time and type of inoculation. This strain was also capable of re-establishing itself following the challenge with other strains, with and without re-challenge. This work represents a "proof of principle" that a defined C. jejuni strain could be used to biologically control circulation of uncharacterised environmental strains in commercial poultry flocks.