# Comparative gastric microbiota profiles in non-ulcer dyspepsia and peptic ulcer patients

## TL;DR

This study compares the stomach microbiota of Turkish patients with non-ulcer dyspepsia and peptic ulcers, finding shifts in bacterial composition linked to the absence of Helicobacter pylori.

## Contribution

The first study from Türkiye comparing gastric microbiota in non-ulcer dyspepsia and peptic ulcer patients, revealing regional microbial patterns.

## Key findings

- H. pylori was more prevalent in peptic ulcer patients (82.6%) than in non-ulcer dyspepsia patients (61.5%).
- In H. pylori-negative cases, oral-origin bacteria like Alloprevotella, Porphyromonas, and Neisseria increased in abundance.
- Microbial shifts in H. pylori-negative patients suggest opportunistic colonization by oral bacteria in gastric disorders.

## Abstract

Recent evidence suggests that the human stomach hosts a diverse microbiota beyond Helicobacter pylori, and that shifts in microbial composition may influence gastric health. In particular, oral-origin bacteria may dominate the gastric niche in the absence of H. pylori, yet their specific roles in different gastroduodenal disorders remain unclear. This study aimed to profile and compare the gastric microbiota composition in Turkish patients with non-ulcer dyspepsia (NUD) and peptic ulcer disease (PUD), in order to better understand microbial profiles potentially associated with gastroduodenal disease.

Ninety-eight patients underwent endoscopic evaluation and were divided into two groups according to the presence or absence of ulcers. Group 1 (n = 52) included individuals with NUD, while Group 2 (n = 46) comprised patients with PUD. Gastric biopsy samples from both groups were analyzed for the relative abundance of H. pylori using quantitative real-time PCR (qPCR), and next-generation sequencing was employed for a comprehensive analysis of the gastric microbiota.

In total, H. pylori DNA was detected in 71.4% (70/98) of the samples, with a significantly higher prevalence in PUD patients (82.6%) compared to NUD patients (61.5%) (p = 0.02). Distinct microbial profiles were observed based on H. pylori status. In NUD patients, Alloprevotella showed significantly higher relative abundance in H. pylori-negative samples (p < 0.05). Among PUD patients, the absence of H. pylori was associated with increased levels of Porphyromonas and Neisseria compared to NUD patients without H. pylori (p < 0.05). These genera, typically associated with the oral cavity, appeared to expand opportunistically when H. pylori was absent.

The absence of H. pylori in gastric disorders was linked to a notable shift in microbiota composition, with increased representation of oral-origin bacteria such as Alloprevotella, Porphyromonas, and Neisseria. These findings, observed in a Turkish patient cohort, may reflect a potentially compensatory or opportunistic microbial shift in H. pylori-negative gastroduodenal disease. As exploratory findings, this study represents the first analysis from Türkiye comparing gastric microbiota profiles in NUD and PUD patients and provides novel regional insight into gastric microbial ecology.