{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T16:37:54Z","timestamp":1789663074637,"version":"4.0.1"},"reference-count":51,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2021,2,26]],"date-time":"2021-02-26T00:00:00Z","timestamp":1614297600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001409","name":"Department of Science and Technology, Ministry of Science and Technology, India","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001409","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:p><jats:italic>Helicobacter pylori<\/jats:italic> infection in stomach leads to gastric cancer, gastric ulcer, and duodenal ulcer. More than 1 million people die each year due to these diseases, but why most <jats:italic>H. pylori<\/jats:italic>-infected individuals remain asymptomatic while a certain proportion develops such severe gastric diseases remained an enigma. Several studies indicated that gastric and intestinal microbiota may play a critical role in the development of the <jats:italic>H. pylori<\/jats:italic>-associated diseases. However, no specific microbe in the gastric or intestinal microbiota has been clearly linked to <jats:italic>H. pylori<\/jats:italic> infection and related gastric diseases. Here, we studied <jats:italic>H. pylori<\/jats:italic> infection, its virulence genes, the intestinal microbiota, and the clinical status of Trivandrum residents (<jats:italic>N<\/jats:italic> = 375) in southwestern India by standard <jats:italic>H. pylori<\/jats:italic> culture, PCR genotype, Sanger sequencing, and microbiome analyses using Illumina Miseq and Nanopore GridION. Our analyses revealed that gastric colonization by virulent <jats:italic>H. pylori<\/jats:italic> strains (<jats:italic>vacAs1i1m1cagA<\/jats:italic>+) is necessary but not sufficient for developing these diseases. Conversely, distinct microbial pools exist in the lower gut of the <jats:italic>H. pylori<\/jats:italic>-infected vs. <jats:italic>H. pylori<\/jats:italic>-non-infected individuals. <jats:italic>Bifidobacterium<\/jats:italic> (belonging to the phylum Actinobacteria) and <jats:italic>Bacteroides<\/jats:italic> (belonging to the phylum Bacteroidetes) were present in lower relative abundance for the <jats:italic>H. pylori<\/jats:italic>+ group than the <jats:italic>H. pylori<\/jats:italic>- group (<jats:italic>p<\/jats:italic> &amp;lt; 0.05). On the contrary, for the <jats:italic>H. pylori<\/jats:italic>+ group, genus <jats:italic>Dialister<\/jats:italic> (bacteria belonging to the phylum Firmicutes) and genus <jats:italic>Prevotella<\/jats:italic> (bacteria belonging to the phylum Bacteroidetes) were present in higher abundance compared to the <jats:italic>H. pylori-<\/jats:italic> group (<jats:italic>p<\/jats:italic> &amp;lt; 0.05). Notably, those who carried <jats:italic>H. pylori<\/jats:italic> in the stomach and had developed aggressive gastric diseases also had extremely low relative abundance (<jats:italic>p<\/jats:italic> &amp;lt; 0.05) of several <jats:italic>Bifidobacterium<\/jats:italic> species (e.g., <jats:italic>B. adolescentis<\/jats:italic>, <jats:italic>B. longum<\/jats:italic>) in the lower gut suggesting a protective role of <jats:italic>Bifidobacterium<\/jats:italic>. Our results show the link between lower gastrointestinal microbes and upper gastrointestinal diseases. Moreover, the results are important for developing effective probiotic and early prognosis of severe gastric diseases.<\/jats:p>","DOI":"10.3389\/fmicb.2021.631140","type":"journal-article","created":{"date-parts":[[2021,2,26]],"date-time":"2021-02-26T07:32:29Z","timestamp":1614324749000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":65,"title":["Low Bifidobacterium Abundance in the Lower Gut Microbiota Is Associated With Helicobacter pylori-Related Gastric Ulcer and Gastric Cancer"],"prefix":"10.3389","volume":"12","author":[{"given":"T. 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J.","family":"Retnakumar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sneha Mary","family":"Alexander","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jijo","family":"Varghese","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sanjai","family":"Dharmaseelan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sivakumar Krishnankutty","family":"Chandrika","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"V. T.","family":"Jissa","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bhabatosh","family":"Das","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G. Balakrish","family":"Nair","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Santanu","family":"Chattopadhyay","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2021,2,26]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0002836","article-title":"Comparative analysis of human gut microbiota by barcoded pyrosequencing.","volume":"3","author":"Andersson","year":"2008","journal-title":"PLoS One"},{"key":"B2","doi-asserted-by":"publisher","first-page":"17771","DOI":"10.1074\/jbc.270.30.17771","article-title":"Mosaicism in vacuolating cytotoxin alleles of Helicobacter pylori. Association of specific vacA types with cytotoxin production and peptic ulceration.","volume":"270","author":"Atherton","year":"1995","journal-title":"J. Biol. 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