Oesophageal bacterial biofilm changes in gastro-oesophageal reflux disease, Barrett's and oesophageal carcinoma: association or causality?

Barrett's oesophagus (BO) and gastro-oesophageal reflux disease (GERD) are precursors of oesophageal adenocarcinoma (OAC). There is an oesophageal biofilm, which changes in disease, but its role in aetiopathogenesis remains unclear. Aim To define the oesophageal microbiota of patients with GERD, BO and OAC compared with controls and to investigate mucosal responses related to the microbiota. Methods Cultural analysis identified the dominant bacterial species from a subset of each disease group. Based on this, molecular techniques were used to define the cohort. Host responses were analysed in tissues and co-culture experiments. Results A total of 111 species belonging to 26 genera were isolated. There was a significant decrease in bacterial counts in the GERD and BO groups for all genera except Campylobacter, which colonised GERD and Barrett's patients in increasing numbers. Campylobacter concisus was the dominant species. This relationship was not seen in the cancer group. Significant increases in IL-18 were seen in GERD and BO colonised by Campylobacter. Conclusions This study defines differences in the oesophageal biofilm in disease states, revealing the emergence of C. concisus as the dominant new colonist in the refluxed oesophagus. We also associate the presence of these bacteria with increased expression of cytokines related to carcinogenesis.