Changes in Gastric Microbial Composition before and after Helicobacter pylori Eradication Therapy

ABSTRACT

Owing to advancements in next-generation sequencing and non-culture-based microbial research techniques, we have recognized that many bacterial taxa other than Helicobacter pylori (H. pylori) are present in the human stomach. Gastric microbial composition depends on gastric diseases, including gastritis, atrophic gastritis, intestinal metaplasia, and gastric cancer. Although H. pylori is a major factor associated with gastric cancer development, other bacterial taxa may affect gastric carcinogenesis. Because the risk of gastric cancer development can be reduced through H. pylori eradication, many investigators have studied the changes in the microbial composition in the stomach after H. pylori eradication. The gastric microbiome in patients with H. pylori infection typically shows abundance of H. pylori and a low microbial diversity index. If we treat H. pylori-infected patients with antibiotics, microbial diversity increases, and the relative abundance also increases in many bacterial taxa. Several studies suggested that the microbial composition in patients with H. pylori infection could be restored by H. pylori eradication therapy; however, there have been inconsistent findings of the abundant bacterial taxa after H. pylori eradication in patients with atrophic gastritis and intestinal metaplasia. More studies are required to reach a definitive conclusion on restoration of the microbial composition after H. pylori eradication according to the severity of gastric inflammation.