Abstract: Objective To investigate the effect of Helicobacter pylori eradication treatment on intestinal flora in children, and to find out the flora that influence the effect of eradication treatment. Methods　Children diagnosed with Helicobacter pylori infection were treated with triple standardized treatment for 14 days, and feces were collected before treatment, 7 days after treatment and 14 days after treatment. The 16S rDNA sequencing was performed. According to the sampling time, the children were divided into pre-treatment group, 7-day treatment group, and 14-day treatment group. According to the treatment effect, the children were divided into treatment success group and treatment failure group. According to the history of the previous radical treatment, the children were divided into retreatment successful group and initial treatment successful group. The differences in flora among different groups were compared. Results　The dominant Phylum of Helicobacter pylori infection in children were Firmicutes, Bacteroidetes, Proteobacteria, Actinomycetes and Verrucomicrobia, and the dominant bacteria were Bacteroides, Faecalibacterium, Escherichia/Shigella, Bifidobacterium, Gemmiger and Klebsiella. Compared with the treatment success group, the relative abundance of Prevotella was increased in the treatment failure group, and the difference was statistically significant (P<0.001). The relative abundance of intestinal microflora changed among before treatment group, 7-day after treatment group and 14-day after treatment group, and the difference was statistically significant (P< 0.05). LEfSe analysis and rank-sum test between groups found that Arcobacter, Barnesia, Coprobacter, Coprococcus, Holdemanella, Thiopseudomonas were higher in the treatment failure group than those in the treatment success group, and the difference was statistically significant (LDA> 2). Compared with initial treatment successful group, the Acinetobacter, Weissella, Sutterella and Providencia in the retreatment successful group were significantly higher (LDA>2), while Alistipes, Erysipelothrix, Clostridium, Faecalibacterium, and Gemmiger were significantly reduced (LDA>2). Conclusions　Helicobacter pylori eradication treatment affects the structure of intestinal flora, which is manifested by the decrease of bacterial diversity and the changes of dominant flora. The growth of enteropathogenic bacteria may affect the eradication effect of Helicobacter pylori and result in the failure of eradication treatment.

Key words: Helicobacter pylori;　antibiotics;　proton pump inhibitors;　16S rDNA sequencing;　intestinal flora