Microbiota in the stomach: New insights

Abstract

Bacteria are sparsely distributed in the stomach due to the gastric microbicidal barrier. Several innate defenses (low pH, migrating motor complex and the entero-salivary circulation of nitrate) as well as external factors (diet, Helicobacter pylori infection, proton pump inhibitors, antibiotics and stomach diseases) have been shown to influence significantly the microbiota composition in the stomach. In recent years new culture-independent technologies have allowed the investigation of the cross talk that occurs between hosts and stomach-associated microflora, which helps us to understand the role of gastric bacterial flora in the gastrointestinal microbiological system, both in physiological and pathological conditions. Here, we reviewed the literatures related to this topic and set the stage for future developments of the field.

In Vivo Analysis of the Viable Microbiota and Helicobacter pylori Transcriptome in Gastric Infection and Early Stages of Carcinogenesis

“…Bik and colleagues found no significant differences in taxonomic composition between H. pylori-negative and -positive subjects, confirming our observations (5), while other studies have found that Helicobacter pylori-negative subjects had higher relative abundances of Firmicutes, Bacteroidetes, and Actinobacteria and that H. pyloripositive individuals had greater abundances of non-H. pylori Proteobacteria, Spirochetes, and Acidobacteria (21). Our data confirm the finding of Firmicutes, Bacteroidetes, and Actinobacteria in several of the subjects with low levels of H. pylori, with Actinobacteria being the dominating phylum in one case.…”

Enlightening discriminative network functional modules behind Principal Component Analysis separation in differential-omic science studies

“…Although PPIs are widely prescribed, they are related to several adverse situations, in particular the development of corpus predominant atrophic gastritis in Helicobacter pylori positive patients, that is a precursor of gastric cancer, and a higher risk of enteric infections2425. These last two conditions are related to the alteration of the gastrointestinal microbiota, therefore this issue has been progressively addressed from a metagenomic perspective2627. The first question of clinical relevance is whether PPIs exert any effect on the gastric bacterial communities, and this was investigated in a study by Williams and collaborators that was still solely based on culturable gastric bacteria28.…”

Analysis of Gastric Microbiota by Pyrosequencing: Minor Role of Bacteria Other Than Helicobacter pylori in the Gastric Carcinogenesis

“…The pattern of phylum composition was identical in all of the four groups including HP (À) groups. This difference can be explained by the diversity in dietary habits [4,14] or by methodological differences such as specific experimental design [4]. Other studies showed that Propionibacterium and Lactobacillus accounted for the majority of cultivable bacteria in human stomach [3,25].…”