Effects of Helicobacter pylori therapy on gut microbiota: a systematic review and meta-analysis

Background: Although indications for evaluation and treatment of Helicobacter pylori (H. pylori) infection are broadening to include primary prevention for gastric adenocarcinoma, potential adverse effects on gut microbiota have been raised. We performed a systematic review and meta-analysis to evaluate the effects of H. pylori therapy on gut microbiota. Methods: PubMed, EMBASE, Cochrane Library and Web of Science (to 4/2021) were searched for studies quantitatively evaluating microbiota before and after H. pylori therapy. Meta-analysis was performed to assess early (< 1 year) and long-term (& GE;1 year) effects on gut microbiota after H. pylori treatment. Subgroup analysis evaluating the effects of H. pylori therapy with addition of probiotics on gut microbiota was also performed. Results: Thirty studies (N=1,218) met the criteria. Early after H. pylori therapy, intestinal microbial diversity was reduced in nearly all studies. At the genus level, reduction in the abundance of Enterococcus, while increase in Lactobacillus, Bifidobacterium, and Bacteroides counts were observed. However, Lactobacillus, Bifidobacterium, Bacteroides, and Enterococcus counts remained stable in patients who received probiotics with H. pylori therapy. At the phylum level, the relative abundance of Actinobacteria and Firmicutes increased after treatment. At & GE;1 year, intestinal microbial diversity normalized in six of seven studies. No differences in the relative abundance of Actinobacteria, Firmicute, Bacteroidetes, and Proteobacteria were observed & GE;1 year after therapy. Conclusion: The impact of H. pylori therapy on gut microbiota appears transient with early changes largely resolving after one year. Probiotics may reduce the early impact of H. pylori therapy on gut microbiota.