Effect of Helicobacter pylori on gastrointestinal microbiota: a population-based study in Linqu, a high-risk area of gastric cancer

Abstract

Objective: Gastrointestinal microbiota may be involved in Helicobacter pylori-associated gastric cancer development. The aim of this study was to explore the possible microbial mechanisms in gastric carcinogenesis and potential dysbiosis arising from H. pylori infection.

Design: Deep sequencing of the microbial 16S ribosomal RNA gene was used to investigate alterations in paired gastric biopsies and stool samples in 58 subjects with successful and 57 subjects with failed anti-H. pylori treatment, relative to 49 H. pylori negative subjects.

Results: In H. pylori positive subjects, richness and Shannon indexes increased significantly (both p<0.001) after successful eradication and showed no difference to those of negative subjects (p=0.493 for richness and p=0.420 for Shannon index). Differential taxa analysis identified 18 significantly altered gastric genera after eradication. The combination of these genera into a Microbial Dysbiosis Index revealed that the dysbiotic microbiota in H. pylori positive mucosa was associated with advanced gastric lesions (chronic atrophic gastritis and intestinal metaplasia/dysplasia) and could be reversed by eradication. Strong coexcluding interactions between Helicobacter and Fusobacterium, Neisseria, Prevotella, Veillonella, Rothia were found only in advanced gastric lesion patients, and were absent in normal/superficial gastritis group. Changes in faecal microbiota included increased Bifidobacterium after successful H. pylori eradication and more upregulated drug-resistant functional orthologs after failed treatment.

Conclusion: H. pylori infection contributes significantly to gastric microbial dysbiosis that may be involved in carcinogenesis. Successful H. pylori eradication potentially restores gastric microbiota to a similar status as found in uninfected individuals, and shows beneficial effects on gut microbiota.

Keywords: bacterial interactions; gastric diseases; gastric pre-cancer; helicobacter pylori - treatment.

Figure 1

Microbial diversity and community structure in gastric biopsy and stool samples. Box plots showing (A1) increased gastric richness index following successful eradication compared with that of baseline and showing no difference to that of Helicobacter pylori negative subjects; (A2) increased gastric Shannon index following successful eradication compared with that of baseline and showing no difference to that of H. pylori negative subjects. Dissimilarities of microbial community structure in gastric biopsies showing (A3) a significant difference before and after successful eradication; (A4) no change before and after failed treatment; (A5) significant differences when the biopsies after successful or failed treatment were compared with H. pylori negative subjects. Box plots showing (B1) no significant change in faecal richness index before and after anti-H. pylori treatment; (B2) no significant change in faecal Shannon index before and after anti-H. pylori treatment. Dissimilarities of microbial community structure in stool samples showing (B3) a significant difference before and after successful eradication; (B4) a significant difference before and after failed treatment; (B5) marginal difference between after successful eradication and H. pylori negative subjects. ^aWilcoxon signed-rank test. ^bLogistic regression adjusted for age, sex and gastric lesion. ^cPERMANOVA test.

Figure 2

Changes in gastrointestinal taxa after anti-Helicobacter pylori treatment. To identify differential microbial taxa after treatment, paired t-tests were performed after arcsine transformation of relative abundance data and Q values were used for multiple testing adjustment with a significance threshold of 0.05. Significantly changed taxa after successful eradication were shown (A) in gastric biopsies at phylum and genus levels with mean relative abundance >1%; (B) in stool samples at all levels with mean relative abundance >1%. Only eight taxa with low baseline abundances (<1%) were changed significantly in stool samples after failed treatment (C).

Figure 3

Gastric microbial dysbiosis is associated with Helicobacter pylori infection and gastric lesions. Box plot showing (A) decreased gastric MDI following successful eradication compared with that of baseline; (B) increased gastric MDIs in CAG and IM/DYS groups compared with that of normal/SG group. Scatter plot showing inverse correlations between (C) gastric MDI and richness index; (D) gastric MDI and Shannon index. ^aWilcoxon signed-rank test. ^bLogistic regression adjusted for age, sex and gastric lesion. ^cKruskal-Wallis test. ^dSpearman correlation analysis. CAG, chronic atrophic gastritis; DYS, dysplasia; IM, intestinal metaplasia; MDI, Microbial Dysbiosis Index; SG, superficial gastritis.

Figure 4

Correlation networks of specific gastric genera in different gastric lesion groups. Spearman correlation analysis was performed to calculate the correlation coefficients (R values) between specific gastric genera. Visualised networks of significant correlations (p<0.05) by Cytoscape V.3.6.1 showed stronger correlation strengths of specific gastric genera in (B) CAG and (C) IM/DYS groups than in (A) normal/SG group. CAG, chronic atrophic gastritis; DYS, dysplasia; IM, intestinal metaplasia; SG, superficial gastritis.