الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
It has been reported that Helicobacter pylori (H. pylori) can cause different diseases such as gastric ulcer, chronic gastritis and gastric adenocarcinoma. As the H. pylori colonized the stomach and destroyed the gastric environment making the stomach a channel between the oral cavity and gut resulting in reshaping of the microbiota of the oral-gut axis. This study aimed to evaluate the changes that accompanied H. pylori infection pre- and post- eradication therapy. This is a comparative study where positive H. pylori infected adult patients were assessed after receiving triple therapy which composed of omeprazole, amoxicillin, and clarithromycin for 14 days. Sixty salivary and fecal samples were collected before and two months post eradication from fifteen patients. DNA was extracted, 16S rRNA gene (V3-V4 region) was sequenced using next‐generation Illumina Miseq sequencing, and data was analyzed using QIIME 2 pipeline. The total read counts 1,912,721 clustered into (8845) operational taxonomic units at 97% similarity. Our oral samples demonstrated that the relative abundance of Firmicutes, Actinobacteria, Bacteroidetes and Patescibacteria declined following treatment while the relative abundance of Fusobacteria, and Proteobacteria increased. On the other hand, regarding stool samples which elucidated that the relative abundance of Firmicutes, Actinobacteria, Proteobacteria, Verrucomicrobia, and Patescibacteria decreased after treatment whereas Bacteroidetes, Euryarchaeota, and Cyanobacteria increased. This study revealed a significant difference in alpha diversity of salivary and fecal samples where the bacterial diversity was less diverse after eradication (Observed, p= 0.018, Chao 1, p =0.00075 and, ACE, p = 0.0062, Simpson, p = 0.0143). Beta diversity analysis based on Bray-Curtis index using Permutational MANOVA (p = 0.001) indicated that salivary and fecal microbial community structure differed before and after H. pylori eradication. Appling LEfSe analysis, defined 84 significant genera at LDA sore ≥ 4 (p <0.05). Our study revealed that H. pylori infection induces significant perturbations and dysbiosis in the oral and gut microbiome which affects human health. H. pylori infection and eradication treatment caused changes in structure and community of both oral and gut microbiota. The shift in microbiota of oral-gut axis focused a great attention on the importance of diagnosis and treatment in H. pylori.