This discovery transformed the management of two chronic relapsing conditions from maintenance symptomatic therapies, and in some cases surgery, to curative treatment with targeted antibiotics. The possibility

that infections by other organisms from the genus Helicobacter are implicated in the pathogenesis of other human diseases is a tantalizing one. The inflammatory bowel diseases (IBD), Crohn’s disease (CD) and ulcerative colitis (UC), demonstrate many similarities to gastric and duodenal ulceration before the discovery of H. pylori, including unexplained onset in previously healthy hosts, a chronic relapsing disease course with no curative treatments, chronic gastrointestinal inflammation Osimertinib price and predisposition to malignant change. In this review, we shall consider the evidence supporting Helicobacter spp. as the pathogenic agents in IBD. We will discuss the relative incompatibility of H. pylori disease Small molecule high throughput screening and IBD, highlighted by the apparent protective effect of prior H. pylori infection on IBD disease risk. We shall review animal variants of IBD, which are both initiated by and associated with Helicobacter spp. infection. We will then review

the Helicobacter organisms associated with human gastrointestinal disease and the molecular evidence for Helicobacter organisms in human IBD. For the purpose of clarity, Helicobacter organisms associated primarily with gastritis or Clostridium perfringens alpha toxin biliary disease are not covered within this article. More than 30 Helicobacter organisms have been described to date (see Fig. 1), but only H. pylori has been

proven to cause human disease. It is inconceivable that H. pylori is the only human pathogen within such a broad genus, and as described below, other candidates are already being investigated. IBD comprises two main conditions: CD and UC. The onset of both conditions occurs at all ages, but with a bimodal distribution with peaks in the late teenage/early adult years (particularly CD) and in late adulthood (particularly UC) (Koehoorn et al., 2006). CD is characterized by transmural inflammation of the gastrointestinal tract at any site from mouth to anus. The disease can affect the mucosa in continuity or include healthy areas between affected sites leading to so-called ‘skip lesions’. Such skip lesions are characteristic of CD and, in addition to the hallmark granuloma on biopsy, they are utilized in differentiating CD from UC. UC affects only the mucosal layer of the gastrointestinal tract and extends in continuity proximally from the rectum (Lennard-Jones, 1989). In UC, the colon is involved exclusively, although ‘backwash’ ileitis can be a feature of extensive disease. The aetiology of both conditions is poorly understood, but genetic, immunological and environmental factors all play a role.