Gastric non-helicobacter pylori helicobacter: Its significance in human gastric diseases

In the post-H. pylori eradication era, the clinical significance of gastric non-H. pylori helicobacters (NHPH; also referred to as H. heilmannii-like organisms and H. heilmannii sensu lato) is gradually increasing. This group of bacteria may inhabit the stomach of domestic and wild animals including cats, dogs, pigs, primates, rodents, cheetahs, and rabbits. NHPH are zoonotic microorganisms, meaning that they may transmit between animals and humans. They may be distinguished from H. pylori regarding their microbiology involving larger cells with more distinct spiral shape and bipolarity, localization in the stomach layer and regional distribution, urease activity and virulence factors, and relation to gastric diseases where gastric NHPH infection is often associated with milder gastritis than H. pylori but higher risk of gastric MALT lymphoma. At present, pure culture of NHPH species remains a challenge, but the full genome sequences of some of the species have been reported. Recent and ongoing prevalence studies indicate a higher clinical relevance of these bacteria than earlier impressions suggested. Current efforts in improving cultivation and detection methodology are contributing to an increased understanding of their microbiology, prevalence, and relevance to human diseases.