Gastric microbiome biodiversity in gastritis patients: Insights from Italian and Chinese cohorts

BACKGROUNDGastric cancer is the fifth leading cause of cancer-related death worldwide, with marked disparities between Eastern and Western populations.Chronic gastritis associated with Helicobacter pylori (H.pylori) infection is a critical precursor to gastric cancer.Understanding the composition of the gastric microbiome in patients with gastritis across geographic regions may provide insights into the epidemiological differences observed. AIMTo characterize and compare gastric microbiome biodiversity among gastritis patients from Eastern and Western populations using unified bioinformatics methods. METHODSWe conducted a systematic search of PubMed, Scopus, and National Center for Biotechnology Information (PROSPERO: CRD42024501792) for studies reporting clinical data and a secondary cross-sectional comparative reanalysis of public 16S ribosomal RNA datasets of patients with gastritis.We reanalyzed the raw FASTQ files using standardized bioinformatics pipelines.We assessed α-diversity (Shannon and Simpson indices), β-diversity (Bray-Curtis dissimilarity), and γ-diversity across taxonomic levels (phylum, order, genus).We used principal coordinates analysis (PCoA) and PERMANOVA to evaluate the effects of H. pylori and histopathology. RESULTSTwo datasets met the inclusion criteria: (1) An Italian cohort (24 patients, 66.7% H. pylori-negative); and (2) A Chinese cohort (104 samples from 62 patients, including gastric mucosa and fluid, 53.2% H. pylori-negative).In the Italian cohort, α-diversity was high (Shannon index > 1) and varied significantly by histopathological severity and H. pylori status.PCoA explained little variance (5.6%-13.7%),and 17 phyla, 50 4 / 37 orders, and 180 genera were identified.PERMANOVA confirmed H. pylori effects at the phylum and genus levels.The Chinese cohort showed greater microbial diversity in gastric fluids than in mucosal samples, with a left-skewed distribution among H. pylori-positive patients.PCoA explained substantially more variance (32.9%-52.9%),identifying 53 phyla, 270 orders, and 1123 genera.PERMANOVA documented H. pylori effects at all taxonomic levels. CONCLUSIONWestern patients with gastritis exhibited microbiome variation strongly associated with histopathological findings and H. pylori status, whereas Eastern patients showed more uniform H. pylori-related distributions but marked compartmentalization across sample types.