Observations on the control of Campylobacter jejuni infection of poultry by 'competitive exclusion'

Various bacteria were isolated aerobically from caecal mucus of campylobacter-free broilers sampled at slaughter. The organisms were mainly presumptive coliform bacteria, enterococci and Micrococcus/Staphylococcus spp. None showed any inhibitory activity against Campylobacter jejuni in a plate assay. On the other hand, adult hens yielded nine strains of Escherichia coli and one strain of Enterococcus faecium that were positive in the plate assay and most of which utilized mucin as an energy source. Coliform bacteria with these properties were also isolated from samples of pig colon and faeces and associated environmental samples. All of the strains from chickens or pigs failed as separate mixtures to protect chicks against a challenge dose of 10(4)-10(5) cfu/bird of C. jejuni. By contrast, chicks dosed with anaerobic preparations of caecal mucus from campylobacter-free adult hens were partly protected against C. jejuni, as shown by values for Protection Factor (mean log(10) of camplylobacters/g in caecal content of control chicks divided by corresponding mean for treated group). Materials from three hens gave values of 7.3, 1.4 and 3.6, respectively.