Helicobacter pylori eradication with bismuth quadruple therapy leads to dysbiosis of gut microbiota with an increased relative abundance of Proteobacteria and decreased relative abundances of Bacteroidetes and Actinobacteria

Background Bismuth quadruple therapy is the treatment of choice for the first‐line therapy of Helicobacter pylori infection in areas of high clarithromycin resistance. Currently, the impact of the promising treatment on gut microbiota remains unclear. Aim To investigate the short‐term and long‐term impacts of bismuth quadruple therapy on gut microbiota. Methods Adult patients with H. pylori‐related gastritis were treated with 14‐day bismuth quadruple therapy. Fecal samples were collected before treatment at week 2, week 8, and week 48. Nucleic acid extraction from fecal samples was performed. The V3‐V4 region of the bacterial 16S rRNA gene was amplified by polymerase chain reaction and sequenced with the MiSeq followed by data analysis using Qiime pipeline. Results Eleven patients received complete follow‐up. Before treatment, the most abundant phyla were Firmicutes (45.3%), Bacteroidetes (24.3%), Proteobacteria (9.9%), and Actinobacteria (5.0%). At the end of bismuth therapy, the relative abundances of Bacteroidetes and Actinobacteria decreased to 0.5% (P