Genome analysis of Campylobacter concisus strains from patients with inflammatory bowel disease and gastroenteritis provides new insights into pathogenicity

Campylobacter concisus is an oral bacterium that is associated with inflammatory bowel disease. C. concisus has two major genomospecies, which appear to have different enteric pathogenic potential. Currently, no studies have compared the genomes of C. concisus strains from different genomospecies. In this study, a comparative genome analysis of 36 C. concisus strains was conducted including 27 C. concisus strains sequenced in this study and nine publically available C. concisus genomes. The C. concisus core-genome was defined and genomospecies-specific genes were identified. The C. concisus core-genome, housekeeping genes and 23S rRNA gene consistently divided the 36 strains into two genomospecies. Two novel genomic islands, CON_PiiA and CON_PiiB, were identified. CON_PiiA and CON_PiiB islands contained proteins homologous to the type IV secretion system, LepB-like and CagA-like effector proteins. CON_PiiA islands were found in 37.5% of enteric C. concisus strains (3/8) isolated from patients with enteric diseases and none of the oral strains (0/27), which was statistically significant. This study reports the findings of C. concisus genomospecies-specific genes, novel genomic islands that contain type IV secretion system and putative effector proteins, and other new genomic features. These data provide novel insights into understanding of the pathogenicity of this emerging opportunistic pathogen.