Roles of Gastric Non‐Helicobacter pylori Helicobacter Species in Gastric Disease Development: A Review

ABSTRACT Gastric Helicobacter species, including Helicobacter pylori and non‐ Helicobacter pylori Helicobacter (NHPH) species, are gram‐negative fastidious bacteria that colonize the stomachs of both humans and animals such as pigs, dogs, cats, and monkeys. The H. pylori infection rate is decreasing due to improved living conditions and increased opportunities for H. pylori eradication therapy in developed countries. However, concerns about NHPH infection‐induced gastric diseases are growing, especially low‐grade gastric mucosa‐associated lymphoid tissue lymphoma. Although NHPH infections have been reported for 30 years, especially H. suis infections, evidence of the correct infection rate, route of infection to humans, and direct and indirect associations with gastric diseases are insufficient. Presently, NHPH infection can be diagnosed using histopathological and immunohistochemical findings, polymerase chain reaction, culture tests, or enzyme‐linked immunosorbent assays. Several basic and clinical studies have begun to report the bacteriologic characteristics and routes of NHPH infection. In addition, the high effectiveness of eradication therapy using a combination of an acid inhibitor and two types of antibiotics, which is the same eradication regimen for H. pylori infection, has been reported. However, evidence on antibiotic resistance, appropriate dosing dosage, or drug type provided by randomized control trials is lacking. Several issues regarding the etiology, virulence, diagnosis, and treatment of NHPH infections should be addressed in the future.