Objective To investigate the characteristics and differences of gastric flora in chronic non-atrophic gastritis and chronic atrophic gastritis associated with Helicobacter pylori (H. pylori).

Methods A prospective study was adopted, and 24 patients with chronic gastritis caused by H. pylori infection were divided into chronic non-atrophic gastritis group (n=18) and chronic atrophic gastritis group (n=6). Characteristics of gastric mucosal flora in both groups were determined, and Alpha and Beta diversity analyses and species correlation analysis were performed.

Results The gastric flora in both groups were mainly consisted of Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, and Fusobacteria. Significant differences in species diversity and abundance were observed between the two groups (ANOSIM analysis, P=0.046). Fusobacterium (P=0.023), Leptotrichia (P=0.047), Prevotella (P=0.016), Sphingomonas (P=0.042), and Treponema (P=0.006) were significantly enriched in the chronic atrophic gastritis group, and H. pylori showed a decreasing trend (P=0.218). Some species of gastric mucosal flora showed negative correlations with H. pylori, and the number of species negatively associated with H. pylori in the gastric mucosal flora of chronic atrophic gastritis was significantly reduced.

Conclusion In the gastric mucosa of chronic atrophic gastritis, the Fusobacterium, Leptotrichia, Prevotella, Sphingomonas, and Treponema are significantly enriched and associated with the progression of chronic gastritis.