Whole genome comparison of Campylobacter jejuni human isolates using a low-cost microarray reveals extensive genetic diversity

Campylobacter jejuni is the leading cause of bacterial food-borne diarrhoea l disease throughout the world, and yet is still a poorly understood pathog en. Whole genome microarray comparisons of 11 C jefuni strains of diverse o rigin identified genes in up to 30 NCTC 11168 loci ranging from 0.7 to 18.7 kb that are either absent or highly divergent in these isolates. Many of t hese regions are associated with the biosynthesis of surface structures inc luding flagella, lipo-oligosaccharide, and the newly identified capsule. Ot her strain-variable genes of known function include those responsible for i ron acquisition, DNA restriction/modification, and sialylation. In fact, at least 21% of genes in the sequenced strain appear dispensable as they are absent or highly divergent in one or more of the isolates tested, thus defi ning 1300 C jejuni core genes. Such core genes contribute mainly to metabol ic, biosynthetic, cellular, and regulatory processes, but many virulence de terminants are also conserved. Comparison of the capsule biosynthesis locus revealed conservation of all the genes in this region in strains with the same Penner serotype as strain NCTC 11168. By contrast, between 5 and 17 NC TC 11168 genes in this region are either absent or highly divergent in stra ins of a different serotype from the sequenced strain, providing further ev idence that the capsule accounts for Penner serotype specificity. These stu dies reveal extensive genetic diversity among C jejuni strains and pave the way toward identifying correlates of pathogenicity and developing improved epidemiological tools for this problematic pathogen.