Alterations in the human gut microbiome associated with Helicobacter pylori infection

Helicobacter pylori infection (HPI) is a prevalent infectious disease associated with gastric ulcer, gastric cancer, and many nongastrointestinal disorders. To identify genes that may serve as microbial markers for HPI, we performed shotgun metagenomic sequencing of fecal samples from 313 Chinese volunteers who had undergone a C14 breath test. Through comparing differences in intestinal microbial community structure between H. pylori-positive and H. pylori-negative individuals, we identified 58 HPI-associated microbial species (P < 0.05, Wilcoxon test). A classifier based on microbial species markers showed high diagnostic ability for HPI (AUC = 0.84). Furthermore, levels of gut microbial vitamin B12 (VB12) biosynthesis and plasma VB12 were significantly lower in H. pylori-positive individuals compared with H. pylori-negative individuals (P < 0.05, Wilcoxon test). This study reveals that certain alterations in gut microbial species and functions are associated with HPI and shows that gut microbial shift in HPI patients may indirectly elevate the risk of VB12 deficiency.