Background: The healthy human esophagus is colonized by bacteria similar to that of the oral mucosa. However, little is known about the microbiome of the esophagus in esophagitis or the possible role of bacteria in the inflammatory response.
Aim: To survey bacterial diversity and compare the microbiome of the esophagus in subjects with gastro-esophageal reflux disease (GERD) and eosinophilic esophagitis (EoE).
Material and methods: Seventeen subjects diagnosed with GERD and 10 with EoE underwent endoscopic examination with brush sampling and biopsies from the oral cavity, upper and lower esophagus. The samples were cultivated on agar plates, and bacterial growth was identified to the genus or species level and semi-quantified.
Results: Significantly higher numbers of bacterial groups or species were found in specimens from the lower esophagus in subjects with EoE compared to subjects with GERD (median 4 (range 1-7) vs. 2 (range 0-6), p < .0014). Sixteen vs. 14 different bacterial groups or species were found in subjects with GERD and EoE, respectively, mostly in sparse or very sparse amounts. Alfa-streptococci (viridans streptococci) were the most common bacteria in both groups. Streptococci were present in all of the EoE-subjects but only in approximately 75% in lower esophagus of the GERD-subjects, regardless of the sampling method.
Conclusion: Subjects with GERD had significantly less bacterial diversity in both oral and esophageal samples than EoE-subjects. Whether this discrepancy might be explained by an effect on the protective mucosal biofilm by the acidic content of the reflux in subjects with GERD remains unclear.
Keywords: Esophagus; bacteria; eosinophilic esophagitis; gastro-esophageal reflux disease; microbiome.