The Relationship Between Bacterial Flora in Saliva and Esophageal Mucus and Endoscopic Severity in Patients with Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease characterized by esophageal dysfunction and eosinophilic inflammation of the esophageal mucosa. In this study, we investigated the bacterial flora in saliva and esophageal mucus in patients with EoE and examined the relationship between EoE disease activity and mucosal cytokine expression, involving patients with active and inactive EoE (A-EoE and I-EoE, respectively). A-EoE was defined as a peak eosinophil count > 15/high-power field, according to the 2025 consensus guidelines. Saliva samples were collected from patients before the endoscopic examination. Brushing samples were collected from the distal esophagus of patients with EoE during endoscopic procedures. The degree of EoE inflammation was assessed using the EoE endoscopic reference score (EREFS). The samples were profiled using the Illumina MiSeq platform. The V3-V4 regions of the 16S rRNA gene (460 bp) were amplified using tailed PCR. Fifty-nine patients were enrolled, including eight with I-EoE, seventeen with A-EoE, and twenty-eight non-EoE controls. Major bacterial genera such as <i>Streptococcus</i>, <i>Prevotella</i>, <i>Veillonella</i>, and <i>Haemophilus</i> were detected in both the oral cavity and esophagus. Compared with the control group, the active EoE group had significantly more <i>Prevotella</i> spp. in the saliva and esophageal mucosa. Conversely, significantly fewer <i>Neisseria</i> spp. were found in the saliva and <i>Streptococcus</i> spp. in the esophageal mucosa of patients with active EoE. The EREFS of EoE and <i>Streptococcus</i> were inversely correlated. This study elucidated the characteristics of bacterial flora in the saliva and esophageal mucosa of patients with EoE.