Correlation between oral microbiome characteristics and clinical phenotypes in patients with GERD and its changes...

Gastroesophageal reflux disease is defined by the reflux of gastroduodenal material into the esophagus, leading to troublesome symptoms and complications. Although the gastrointestinal microbiome has been increasingly implicated in gastroesophageal reflux disease pathogenesis, existing research has largely centered on esophageal and intestinal microbiota. The alterations and clinical relevance of the oral microbiome in gastroesophageal reflux disease remain underexplored. Therefore, this study was designed to: (1) systematically compare the oral microbiome structure between gastroesophageal reflux disease patients and healthy controls, and to examine the correlations between differentially abundant microbial taxa and key clinical phenotypes; (2) longitudinally assess the dynamic changes in the oral microbiome after anti-reflux surgery.

We conducted a study integrating a case-control design with a longitudinal self-controlled component. Initially, 40 patients and 20 healthy volunteers were enrolled. Following exclusions based on diagnostic confirmation, 36 gastroesophageal reflux disease patients comprised the preoperative group (Group Pre), and 17 age-, gender-, and BMI-matched healthy volunteers served as controls (Group HC). Non-stimulated whole saliva samples were collected from all participants. A subgroup of 18 patients from Group Pre subsequently underwent laparoscopic fundoplication. Their saliva samples collected 3 months postoperatively constituted the postoperative group (Group Post) for longitudinal comparison. The V3-V4 hypervariable regions of the bacterial 16S rRNA gene were amplified and sequenced using high-throughput sequencing. Sequencing data were processed and analyzed with bioinformatics pipelines to evaluate α- and β-diversity. Differential microbial features across groups were identified using Linear Discriminant Analysis Effect Size. Correlations between microbial relative abundance and clinical parameters were assessed via Spearman's rank correlation. Changes in the microbiome following surgery were evaluated using paired non-parametric statistical tests.

(1) Cross-sectional comparisons: no significant differences were observed in α-diversity indices (ACE, Chao1, Shannon, and Simpson; all P > 0.05) of the oral microbiome between GERD patients (Group Pre) and healthy controls (Group HC). In contrast, β-diversity analysis indicated a significant overall structural disparity between the groups (PERMANOVA, R ² = 0.044, P = 0.003). Linear Discriminant Analysis Effect Size (LEfSe) identified discriminant taxa distinguishing the two groups, with genera like Alloprevotella and Veillonella being enriched in Group Pre, and Streptococcus enriched in Group HC. Furthermore, Spearman correlation analyses identified significant associations between specific genera and clinical parameters: the relative abundance of Veillonella showed a positive correlation with the gastroesophageal reflux disease questionaire score (r = 0.347, P = 0.038), and that of Alloprevotella correlated positively with the severity of esophagitis as graded by the Los Angeles classification (r = 0.335, P = 0.046).(2) Longitudinal analysis revealed that bacterial genera such as Veillonella, which were associated with phenotypes in cross-sectional studies, did not show significant changes in the oral microbiota between the Pre- and Post- groups. The most characteristic alteration was that the relative abundance of the pro-inflammatory genus Fusobacteriumwas succeeded by Selenomonas, a genus with potential metabolic benefits.

Our study demonstrates that gastroesophageal reflux disease is characterized by a specific oral dysbiosis, with the abundance of particular bacterial taxa correlating with clinical disease severity. Although laparoscopic anti-reflux surgery did not drastically alter the global oral microbiome architecture, it induced a targeted ecological shift. This shift was marked by the suppression of pro-inflammatory taxa, an increase in potentially beneficial commensals, and a trend toward restored α-diversity. These findings suggest that laparoscopic anti-reflux surgery may facilitate a shift of the oral microbiome toward a healthier ecological state following restoration of the anti-reflux barrier function. This observation provides a new microbiological perspective for understanding the broader physiological impact of anti-reflux surgery.