To analyse the saliva microbial abundance and composition by 16s rRNA sequence during Helicobacter pylori (H.pylori) eradication. Descriptive study. Hebei University of Chinese Medicine, Hebei Provincial Hospital of Traditional Chinese Medicine, from March 2019 to January 2020. The saliva microbial were analysed before and after the bismuth-containing quadruple therapy. A total of ten saliva samples (three groups) were enrolled in the study. The authors used the linear discriminant analysis

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... ct size (LEfSe) method and Welch's t-test for comparative analysis to identify which taxa could be significantly affected in three groups. H.pylori 16S rRNA gene sequence was not detected in the ten saliva samples. The abundance of Prevotella_sp._oral_clone_P4PB_83_P2 from healthy adults was higher than H.pylori-positive patients. Moreover, after the bismuth-containing quadruple therapy, the diversity and richness of saliva bacteria reduced. Lautropia, Burkholderiales, uncultured bacterium, Burkholderiaceae, and Actinomyces were enriched in H.pylori-positive patient samples after the bismuth-containing quadruple therapy. The diversity and richness of salivary microbiome were reduced in H.pylori-positive patient, and bismuth-containing quadruple therapy affected oral microbiota. Key Words: Helicobacter pylori, Saliva, Microbiota, RNA, Bismuth.