Campylobacter concisus

Campylobacter concisus is a Gram-negative, highly fastidious, mesophilic bacterium that grows under both anaerobic and microaerobic conditions with the presence of hydrogen significantly aiding growth.[1] Motile, with either unipolar or bipolar flagella, the organisms have a characteristic spiral/corkscrew appearance and are oxidase-positive.[2][3][4] Although the human oral cavity is the natural colonization site of the bacterium, C. concisus may also colonize the intestinal tract of some individuals.[5] In particular, several studies have reported higher intestinal prevalence of C. concisus in patients with IBD compared to healthy controls,[6][7] which has led to current speculation of the bacterium's implication in the induction of Crohn's disease.

Campylobacter concisus
Scientific classification
Domain:	Bacteria
Phylum:	Campylobacterota
Class:	"Campylobacteria"
Order:	Campylobacterales
Family:	Campylobacteraceae
Genus:	Campylobacter
Species:	C. concisus
Binomial name
Campylobacter concisus Tanner et al., 1981

A number of studies have defined C. concisus to be composed of two phenotypically identical, yet genomically distinct genomospecies by analysis of amplified fragment length polymorphisms (AFLP), housekeeping genes and a PCR method targeting the polymorphisms of C. concisus 23S rRNA gene.[8][9][10][11][12][13] The two genomospecies appear to harbor different levels of enteric pathogenic potential, with oral C. concisus strains that were invasive to human epithelial cell line (Caco2) found only in Genomospecies-2 (GS2).[14][15]

Recently, a C. concisus molecular marker csep1, particularly the csep1 gene with a six-nucleotide insertion (csep1-6bpi) was found to be associated with active Crohn's disease, and pSma1 plasmid was found to be associated with severe ulcerative colitis.[16][17] The csep1 gene can be located in either the pICON plasmid or the chromosome.