Introduction:

Obesity has been linked to alterations in the gut microbiota, which may influence gastrointestinal inflammation and metabolic health. While Helicobacter pylori is a well-known cause of gastritis, the microbial landscape in H. pylori-negative gastritis, especially in individuals with obesity, is less understood.

Objective:

To investigate whether adults with obesity and H. pylori-negative gastritis exhibit distinct gastric microbiota signatures compared to matched controls without gastritis.

Methods:

• Design: Case-control study.
• Participants: Adults with obesity, stratified into two groups:
• Cases: Those with histologically confirmed H. pylori-negative gastritis.
• Controls: Obese individuals without gastritis.
• Analysis: Gastric biopsy samples were analyzed for microbial composition using high-throughput sequencing. Comparative analyses were conducted to identify microbial differences between groups.

Results:

1. Participants: 67 adults included
   1. Gastritis group: 38
   2. Non-gastritis group: 29
2. Microbial Diversity:
   1. Alpha diversity (evenness and Shannon indexes) was lower in the gastritis group.
   2. Beta diversity (weighted UniFrac distance) showed distinct microbial community structure in the gastritis group compared to non-gastritis.
3. Microbial Composition: The gastritis group had higher relative abundances of:
   1. Families: Micrococcaceae, Streptococcaceae, Leuconostocaceae
   2. Genera: Streptococcus, Weissella, Cryptobacterium
4. Functional Pathways: The gastritis group showed enrichment in microbial pathways related to:
   1. Toluene degradation
   2. Heterolactic fermentation
   3. Biosynthesis of secondary metabolites like ergothioneine and terpenoids
5. Metabolic Outcome:
   1. Higher total cholesterol levels were observed 1 year after surgery in the gastritis group compared to the non-gastritis group.
   2. However, no significant within-group changes in cholesterol were seen from baseline to 1 year in either group.

Conclusion:

Results suggest that alterations in the gastric microbiome are associated with non-atrophic chronic gastritis in individuals with obesity, independent of Helicobacter pylori infection. These findings highlight the potential role of microbiota in gastric inflammation and may open avenues for microbiome-targeted interventions in obesity-related gastric disorders.

ECO, 11-14 May 2025, Malaga, Spain