P464. Dysbiosis in mucosally adherent microbiota at surgery and in post-endoscopic recurrence at 6 and 12 months – a longitudinal prospective evaluation in Crohn's disease

A. Murugananthan1, P. Tozer1, D. Bernardo1, A. Hart2, S. Knight1, K. Whelan3, H.O. Al-Hassi1, N. Arebi2

1Antigen Presentation Research Group, Imperial College, London, United Kingdom; 2St Mark's Hospital, Department of Gastroenterology, London, United Kingdom; 3King's College Hospital, London, United Kingdom

Background: Alterations of gut microbiota (dysbiosis) are involved in Crohn's Disease (CD) pathogenesis. We aimed to study whether altered balance of bacterial species is associated with postoperative CD endoscopic recurrence.

Methods: Samples were collected from inflamed and non-inflamed surgically resected small bowel in CD patients at ileo-caecal resection (ICR). The patients were followed longitudinally and colonoscopy was performed at 6 and 12 months. Biopsies from the neo-terminal ileum were collected and endoscopic recurrence graded by Rutgeerts score (RS). Samples were hybridised with oligonucleotide probes targeting the microbial 16S rRNA of panbacteria, Escherichia coli, Bacteroides–Prevotella, Faecalibacterium prausnitzii, Clostridium coccoides, Eubacterium rectale and bifidobacteria. The hybridised mucosa associated microbiota were identified and quantified. Endoscopic recurrence was classified as normal/mild (Rutgeert score {RS} ≤i1) or severe (RS ≥i2).

Results: Fifteen patients underwent ICR (10 female). Nine patients had clinical risk factors for recurrence (6 smokers, 4 with fistulating disease and 2 with recurrent resection – multiple risk factors present in 3 patients). High-risk patients received azathioprine post operatively. In surgical specimens, mucosally adherent Escherichia coli 1531 numbers were higher in inflamed compared with non-inflamed SB (Paired samples, p = 0.0015). No differences were noted with other 16S rRNA probes. Eleven patients underwent 6‑month and 4 underwent 12-month colonoscopies. Patients with Rutgeerts scores ≥i2 had lower bifidobacteria numbers compared with patients with scores ≤i1 both at 6 months (p = 0.023) and overall (p = 0.026).

Conclusions: Mucosally adherent Escherichia coli are prevalent in pre-operative inflamed mucosa. Post-operative endoscopic recurrence was associated with lower numbers of protective bifidobacteria. These differences in microbiota implicate a potentially diverse and dynamic bacterial profile with progressive inflammation in CD.