Gastric microbiota in patients with gastric MALT lymphoma according to Helicobacter pylori infection

Background: Gastric Mucosa Associated Lymphoid Tissue lymphoma (GML) development is triggered by Helicobacter pylori (H. pylori) infection. Little is known about the impact of H. pylori infection on gastric microbiota. It is also unclear whether patients with H. pylori-negative GML are independent of chronic bacterial stimulation.Aim: To study gastric microbiota of patients with GML and controls.Methods: The gastric microbiota was retrospectively investigated using 16S rRNA gene sequencing in 33 patients with GML (11 H. pylori-positive and 22 H. pylori-negative), 23 with remitted and 17 refractory GML and 28 controls. Differences in microbial diversity, bacterial composition and taxonomic repartition were assessed.Results: In H. pylori-positive samples from GML and control patients, diversity indexes were decreased and bacterial composition disclosed significant differences, compared with H. pylori-negative samples. There was no change in diversity and bacterial composition between GML and control patients taking into account H. pylori status. Differential taxa analysis identified 12 significantly altered gastric genera significantly associated with H. pylori-negative GML: the abundances of Streptococcus, Actinobacillus, Haemophilus, Thermicanus, Lactobacillus and Chryseobacterium were increased while the abundances of Veillonella, Atopobium, Leptotrichia, Catonella, Filifactor and unidentified Gbacteria were decreased. In patients with remitted GML, the family Pasteurellaceae was significantly more abundant than in refractory patients, while Atopobiaceae and Lachnospiraceae were significantly more abundant in refractory patients.Conclusion: Detailed analysis of the gastric microbiota revealed significant changes in the bacterial composition of the gastric mucosa in patients with GML that may have a role in gastric lymphomagenesis but not any new pathobionts.