Campylobacteriosis is the leading foodborne bacterial diarrheal illness in many countries, with up to 80% of human cases attributed to the avian reservoir. The only control strategies currently available are stringent on-farm biosecurity and carcass treatments. Heritable differences in the resistance of chicken lines to Campylobacter colonization have been reported and resistance-associated quantitative trait loci are emerging, although their impact on colonization appears modest. Recent studies indicated a protective role of the microbiota against colonization by Campylobacter in chickens. Furthermore, in murine models, differences in resistance to bacterial infections can be partially transferred between lines by transplantation of gut microbiota. In this study, we investigated whether heritable differences in colonization of inbred chicken lines by Campylobacter jejuni are associated with differences in cecal microbiota. We performed homologous and heterologous cecal microbiota transplants between line 6₁ (resistant) and line N (susceptible) by orally administering cecal contents collected from 3-week-old donors to day-of-hatch chicks. Recipient birds were challenged (day 21) with C. jejuni 11168H. In birds given homologous microbiota, the differential resistance of lines to C. jejuni colonization was reproduced. Contrary to our hypothesis, transfer of cecal microbiota from line 6₁ to line N significantly increased C. jejuni colonization. No significant difference in the overall composition of the cecal microbial communities of the two lines was identified, although line-specific differences for specific operational taxonomic units were identified. Our data suggest that while heritable differences in avian resistance to Campylobacter colonization exist, these are not explained by significant variation in the cecal microbiota.IMPORTANCECampylobacter is a leading cause of foodborne diarrheal disease worldwide. Poultry are a key source of human infections, but there are currently few effective measures against Campylobacter in poultry during production. One option to control Campylobacter may be to alter the composition of microbial communities in the avian intestines by introducing beneficial bacteria, which exclude the harmful ones. We previously described two inbred chicken lines which differ in resistance to intestinal colonization by Campylobacter Here, we investigated the composition of the microbial communities in the gut of these lines and whether transferring gut bacteria between the resistant and susceptible lines alters their resistance to Campylobacter No major differences in microbial populations were found, and resistance or susceptibility to colonization was not conferred by transferring gut bacteria between lines. The data suggest that gut microbiota did not play a role in resistance to Campylobacter colonization, at least in the lines used.

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