Effect of the PSMR gene mutations on Campylobacter colonization and transmission in chickens. (A) Colonization levels of single-mutant strains KO39Q and KO73Q in comparison with the wild-type strain NCTC11168. (B) Colonization levels of double mutant DKO01Q in comparison with the wild-type strain NCTC11168. In (A) and (B), cecal contents were collected from chickens necropsied on DAI 5, 10, and 15. Each symbol represents data from a single bird and bars indicate the mean ± SD for each group. Dashed lines indicate the detection limit of the direct plating method. (C) and (D): Co-mingling experiment demonstrating the transmission of C. jejuni from seeder birds (n = 3 in each group) to naive (non-inoculated) birds. (C) The percentage of naive birds (n = 10 for the wild type group and n = 9 for DKO01Q group) positive for C. jejuni after comingling with seeder birds inoculated with NCTC11168 and DKO01Q, respectively. (D) Cecal colonization levels of the wild-type strain and DKO01Q strains in naive birds co-mingled with the seeder birds. The birds were euthanized at 9 and 12 days after initiation of co-mingling. Each symbol represents the colonization level of a single bird and the horizontal bars indicate the mean and standard error for each group.