Gastric bacteria as potential biomarkers for the diagnosis of atrophic gastritis

Background Identification of the risk factors for atrophic gastritis (AG) and prevention of further deterioration of the gastritis are effective approaches to reduce the incidence of gastric cancer. Previous studies found that dysbiosis has been implicated in a wide range of diseases, while the role of gastric bacteria as a biomarker for AG has not been explored. Methods and Results Gastric juices from cases with non-atrophic gastritis (NAG) and AG were collected for investigation of bacterial composition and function. The β-diversity of microbiota exhibited a significant reduction in AG samples compared with that in NAG samples. Differential abundance analysis revealed that a total of 23 predicted species changed their distributions; meanwhile, all obligate anaerobic bacteria with a relatively high abundance lowered their contents in AG samples. Additionally, the correlation analysis indicated a clear shift in bacterial correlation pattern between the two groups. Functional interrogation of the gastric microbiota showed that bacterial metabolisms associated with enzyme families, digestive system, and endocrine system were downregulated in AG samples. The compositional dissection of “core microbiota” exhibited that oral pathogens, including Porphyromonas gingivalis , Campylobacter gracilis , and Granulicatella elegans , were magnified in AG samples, suggesting that oral diseases may be a trigger factor for early exacerbation of gastritis. Then, the differentially expressed bacteria were used as diagnostic biomarkers for the random forest classifier model for group prediction. Conclusions The results showed that bacterial biomarkers could distinguish AG patients from NAG cases with an accuracy of 90% at the genus level.