Alterations of Enteric Microbiota in Patients with a Normal Ileal Pouch Are Predictive of Pouchitis.

Objective: To examine whether patients with a mature normal pouch [> 1 year post ileostomy closure] have microbial stool characteristics that can predict pouch inflammation.

Design: Patients undergoing pouch surgery were recruited prospectively. Microbiota analysis of faecal samples was by 16S rRNA gene pyrosequencing. All patients had a normal pouch at baseline [T1]. Those without pouchitis during the first year of follow-up [T2] comprised the 'Normal Pouch-sustained' group and those who had experienced an episode of pouchitis comprised the 'Pre-Pouchitis' group.

Results: Twenty patients were recruited (age 53.6±13.1 years, pouch age [time from ileostomy closure] 8.1±5.1 years). Seven patients developed pouchitis during follow-up [within 265±93.6 days] and they were assigned to the Pre-Pouchitis group at T1: they had a decreased microbial diversity at T1 compared with the Normal Pouch-sustained patients [n = 13]. The Shannon diversity index for the Pre-Pouchitis patients was 3.4 vs 4.23 for the Normal Pouch-sustained patients [p = 0.011]. There were no substantial group differences in high taxonomic levels [order or above]. The genus Ruminococcus was significantly decreased in the Pre-Pouchitis patients' samples compared with those of the Normal Pouch-sustained patients (0.19% vs 0.78%, respectively, false discovery rate [FDR] = 0.05). The linear discriminant analysis with effect size estimation algorithm revealed that Lachnospira and Coprococcus genera were also decreased among Pre-Pouchitis patients compared with Normal Pouch-sustained patients [0.6% vs 1.95% and 2.1% vs 4%, respectively].

Conclusions: Patients with a normal mature pouch may be predisposed to acute pouchitis when faecal microbial diversity and certain microbial groups are decreased. These findings may aid in risk stratification of those patients.