The discovery of Helicobacter pylori sparked a revolution in the understanding and management of peptic ulcer disease and gastric cancer. Other Helicobacter species are recognized as important pathogenic agents in colitic diseases of rodents and primates, in particular Helicobacter bilis, Helicobacter fennelliae, Helicobacter hepaticus and Helicobacter trogontum. Helicobacter bilis and H. hepaticus are now routinely used to initiate rodent models of inflammatory bowel disease (IBD), particularly in immunocompromised hosts. Molecular evidence exists linking various non-pylori Helicobacter spp. with human IBD; however, attempts to culture organisms in this disease cohort have proved unsuccessful to date. Attributing causation has therefore proved elusive. Seven enterohepatic, non-pylori Helicobacter organisms have been successfully cultured from humans, namely Helicobacter canadensis, Helicobacter canis, Helicobacter cinaedi, H. fennelliae, Helicobacter pullorum, Helicobacter winghamensis and Helicobacter sp. flexispira taxon 8 (now classified as H. bilis). Of these, H. cinaedi and H. fennelliae are the closest to fulfilling Koch's postulates as causative agents in homosexual proctitis. The possibility that novel Helicobacter organisms have a role in the initiation of human IBD warrants further consideration and targeted investigations.
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