The data obtained supported both of these hypotheses. Furthermore, during the course of these experiments, it became apparent that dietary factors can also influence disease expression in this mouse model. Results Five

experiments are reported here. Experiment 1 comprised genetic comparisons of seven C. jejuni strains by multilocus sequence typing and restriction fragment polymorphism analysis of known and putative virulence loci. Experiment 2 comprised four serial passages of each of five C. jejuni strains in C57BL/6 IL-10-/- mice. The final passage in experiment 2 also included (1) a comparison of passaged strains with unpassaged C. jejuni 11168 and (2) a comparison of mice infected with PF-02341066 solubility dmso unpassaged C. jejuni 11168 kept on an ~12% fat breeder diet and mice infected with unpassaged C. jejuni 11168 experiencing VRT752271 concentration a transition from the ~12% fat breeder diet to an ~6% fat maintenance diet just prior to inoculation. Experiment 3 was suggested by

the results of experiment 2 and comprised a whole ORF microarray comparison of the gene content of C. jejuni strains 11168 and NW. Experiment 4 was also suggested by the results of experiment 2 and comprised a short term (48 hour) infection study of passaged and unpassaged C. jejuni 11168 strains to determine whether there were any differences in ability of the strains to cause enteritis immediately after infection. Experiment Immune system 5 was suggested by the results of the dietary comparison included in the final passage of experiment 2 and comprised a comparison of mice infected with unpassaged C. jejuni 11168; mice were kept on the ~12% fat diet throughout the experiment, were kept on the ~6% fat diet throughout the experiment, or were subjected to a transition from

the ~12% fat diet to the ~6% fat diet just prior to inoculation. C. jejuni strains used in this study were genetically variable in both housekeeping genes and virulence determinants (experiment 1) The seven C. jejuni strains used in this study are listed in Table 1. They represent six MLST sequence types in six clonal complexes and were chosen in part so as to span the genetic diversity of the strains characterized by MLST by Sails et al. [41]. An MLST-based neighbor-joining tree displaying the genetic relationships of these strains to each other and to reference strains for the major C. jejuni clonal complexes is shown in Figure 1A; the tree includes MLST sequences for reference strains of major clonal complexes established by Wareing et al. [42]. Sequences for the reference strains and all strains used in this study except strain NW were obtained from the Campylobacter jejuni MLST database [7]. MLST typing of strain NW was carried out in our laboratory (GenBank accession numbers FJ361183 through FJ361189) and the clonal complex determined using the Campylobacter jejuni MLST database.