Metagenomic analysis of the intragastric and oral microbiome associated with gastric carcinogenesis after Helicobacter pylori eradication.

BACKGROUND: Few reports have investigated bacterial microbiome in relation to gastric cancer after eradication of Helicobacter pylori (H. pylori). We aimed to conduct a genetic analysis of the gastric and oral microbiome, to identify its association with development of gastric cancer after H. pylori eradication. METHODS: The patients with prior endoscopic submucosal dissection (ESD) history after eradication (cancer patients) and control patients after eradication who underwent upper gastrointestinal endoscopy at Kawasaki Medical School Hospital from May 2021 to March 2023 were enrolled. Saliva and gastric mucus samples were collected and profiled by 16S rRNA gene amplicon sequencing. RESULTS: The subjects consisted of 24 cancer patients and 27 controls. The abundance of the genus Rothia in gastric mucus of the cancer patients was significantly higher compared to the controls. Conversely, the genus Parvimonas was significantly less abundant in the cancer patients. These differences in salivary samples between the two groups were not observed. The abundance of the genus Parvimonas in the gastric mucous was associated with the gastric atrophy, but genus Rothia was not. CONCLUSIONS: Genus Rothia may have some influence on carcinogenesis following H. pylori eradication.