Abstract:Objective By using high throughput sequencing to detect the intestinal flora of patients with gastric cancer, and to explore its distribution and the characteristics of flora function. Methods According to the inclusion and exclusion criteria, 42 patients with gastric adenocarcinoma admitted to the First Affiliated Hospital of Hebei North University from 2019 to 2021 were selected as the research subjects, and 30 gender-and age-matched healthy volunteers were recruited as the control group. Fecal samples were collected for extracting DNA in two groups. Microbial populations were analyzed using 16S ribosomal DNA amplicon pyrosequencing. PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was used to identify functional differences of flora. Results Compared with control group, the abundance of Bacteroidetes decreased, while the abundance of Proteobacteria and Actinobacteria increased significantly in research group (t=4.491, 1.491, 3.369, P<0.05). The results of α diversity analysis showed that Chao1 index was increased, while Shannon diversity index was decreased in gastric cancer patients (t=10.884,9.953, P<0.01). Principal co-ordinates analysis (PCoA) showed the differences in the structure of flora between two groups. Linear discriminant analysis(LDA) effect size (LEfSe) analysis showed that the abundance of Escherichia-Shigella in gastric cancer patients was significantly higher than that in control group,while Bacteroides and Lactobacilli were significantly lower than those in control group (LDA=3, P<0.05). Kyoto Encyclopedia of Genes and Genomes (KEGG) showed the differences in gut microbiota metabolism between two groups. Conclusion The diversity and structure of intestinal flora in patients with gastric cancer are different from those in healthy people, suggesting that intestinal flora may be involved in the occurrence of gastric cancer.