Comparative study of gastric microbiota between patients with autoimmune gastritis and those with atrophic gastritis.

Fundamental treatments for autoimmune gastritis (AIG) have not yet been established; thus, analyzing AIG pathogenesis in detail to obtain useful information for prognosis prediction and treatment is crucial. This study explored bacteria involved in AIG pathogenesis by focusing on the gastric microbiota composition. Gastric biopsy tissues were collected endoscopically from the gastric corpus and antrum of patients with AIG and chronic gastritis. Total DNA was extracted from gastric biopsy specimens and used for 16S rRNA gene amplicon sequencing analysis. Principal coordinate analysis of diversity using the weighted UniFrac distance revealed that following Helicobacter pylori eradication, the gastric bacterial composition of patients with AIG differed significantly from that of patients with chronic gastritis, exhibiting decreased Shannon index, Pielou's evenness, and Simpson index of alpha diversity. The gastric microbiota of patients with AIG was characterized by an increased abundance of the genus Streptococcus and a reduced abundance of the genus Prevotella compared with that of patients with chronic gastritis.