jejuni 11168 infected mice: from grade 1 in previous experiments to grade 2 after serial passage. The tests for trends were statistically significant for strains 11168 (χ2 = 16.47; d.f. = 1; 0.00001 < P < 0.0001), D0835 (χ2 = 18.25; d.f. = 1; 0.00001 < P < 0.0001), and D2600 (χ2 = 16.90; d.f. = 1; 0.00001 < P < 0.0001). The test was not significant for strain D2586 (χ2 = 2.14; d.f. = 1; 0.14 < P < 0. 15) and could not be conducted for strain NW since there were no NW-infected

mice having histopathology scores in grade 2. DNA:DNA microarrray comparison of C. jejuni strains 11168 and NW (experiment 3) revealed differences between the strains Because strain NW was able to colonize C57BL/6 IL-10-/- mice but did not cause severe enteritis in the initial infection and did not evolve to a higher level of pathogenicity during repeated passages, we elected

to examine its genetic content more closely by comparing it to the selleck inhibitor highly pathogenic strain 11168 using an in-house full open reading frame (ORF) microarray with coverage of 95% of the C. jejuni 11168 genome [50]. The microarray was constructed using PCR products synthesized using primers for sequence-validated ORFs developed by Parrish et al. [51] and genomic DNA from strain 11168 (See NCBIGEO series number GSE13794 for a description of chip NVP-LDE225 solubility dmso manufacture.) We hypothesized that known virulence determinants would be among the genes present in strain 11168 but absent from strain NW. Sixty-nine C. jejuni 11168 ORFs were identified as possibly absent in strain NW by Genomotyping (GACK) analysis of microarray data [52]. Fifty-four of the 69 ORFs were confirmed to be absent or strongly divergent by PCR assay (Additional file 1, Table S2); PCR products of the appropriate size were obtained for thirteen of the remaining ORFs. Many of the ORFs missing in strain NW belong to complex loci encoding surface structures known both to be involved in C. jejuni pathogenesis and to be highly variable in gene content (flagellin, 8 ORFs; capsule, 11 ORFs; LOS, 1 ORF

(gmhA); [53]). Nine additional ORFs may encode membrane proteins; three may encode DNA restriction and modification proteins. Four periplasmic proteins were absent or strongly divergent C-X-C chemokine receptor type 7 (CXCR-7) in strain NW, along with seven ORFs having other known or putative functions and 11 ORFs encoding hypothetical proteins for which no function could be suggested [53]. For two ORFs, Cj 0987c (putative integral membrane protein) and Cj0874c (possible cytochrome c protein), strain NW DNA yielded PCR products smaller than those produced from strain 11168 DNA. Sequencing of the PCR products from strain NW showed that Cj0987c had a 649 bp deletion (nucleotides 121–770 of Cj0987c from strain 11168) compared to strain 11168. ORF Cj0874c in strain NW had a 182 bp deletion (nucleotides 212–393 of Cj0874c from strain 11168) compared to strain 11168.