Influence of Mechanical Bowel Preparation on GI Microbiota

The mechanical bowel preparation (BP) procedure, which directly precedes colonic endoscopy, results in a significant reduction in reported symptoms for several bowel disorders (eg irritable bowel syndrome (IBS )), but as yet, there is little research-based supporting evidence. This proposal will use a robust experimental design to explore both the composition of the microbiota, and importantly, its metabolic activity to assess interactions with human hosts following BP. The aim of this pilot study is to generate data demonstrating the destabilising effects of BP on both the composition and metabolic activity of the gut microbiota.

If the hypothesis is proven, this study will show that BP generates a 'window of opportunity' in which to influence the subsequent re-establishment of the microbiota. This is with the eventual aim of correcting dysbiosis and preventing the development of symptomatic uncomplicated diverticular disease in patients with diverticulosis.

Background Diverticular disease, characterised by weakness of the supporting connective tissue of the wall of the colon leading to the formation of diverticula1, is somewhat neglected and does not receive scientific attention that other inflammatory gut disorders have. Despite this condition affecting 50% of our aging population, approximately 1/5 of which will develop debilitating symptomatic uncomplicated diverticular disease (SUDD)2, there is a paucity of knowledge in this field.

The factors determining the transition from asymptomatic diverticulosis to SUDD are unclear. However, the gut microbiota has been implicated in a recent small-scale study which correlated diverticulosis with depletion of Clostridium cluster IV. Clostridium cluster IX, Fusobacterium and Lactobacillaceae, all of which can exert an anti-inflammatory effects. Patients who present with left-side non-specific abdominal pain and diarrhoea are assessed by colonic endoscopy. A small-scale study showed that this procedure also resulted in a significant reduction in Lactobacillaceae in the control population after 1 month (n=10).

BP is received 14 and 20 hours prior to colonoscopy and involves oral administration with a variety of stimulant laxatives (eg Moviprep - polyethylene glycol) resulting in severe diarrhoea and complete clearance of faecal matter from the bowel. It is likely that this BP is implicated in any reduction in reported symptoms as opposed to the endoscopic procedure itself, although putative underlying mechanisms have yet to be identified.

Hypothesis: Bowel preparation for endoscopy will destabilise the gut microbiota in patients with diverticulosis. Re-establishment of this microbiota follows an altered developmental trajectory resulting in sustained changes to the composition of the microbiota. Furthermore, these observed changes will have functional consequences as identified through altered metabolic interactions at the microbe-host interface.

Aims and objectives:

1. Quantify sustained observational changes which occur within the functional groups of the gut microbiota following BP (HTP FISHflow technology).
2. Functional consequences of such changes to host metabolism, host-microbe co-metabolism and short chain fatty acid production will be assessed (nuclear magnetic resonance spectroscopy and gas chromatography respectively).
3. Statistical data integration techniques will identify links between the altered microbiota and metabolic profiles to begin to determine the mechanisms underlying the influence of the gut microbiota in diverticulosis .
4. The outputs above will identify whether a 'window of opportunity' occurs following BP which could be exploited to rectify dysbiosis as a basis for a later larger-scale study.

Experimental design

In order to assess the effects of BP on the colonic microbiota in diverticulosis, post-menopausal women with mild non-specific left sided abdominal pain and diarrhoea, who have been referred to the colorectal unit at the Royal Berkshire Hospital , will be recruited by the applicants (KT, PC). Patients who have not received antibiotics in the previous 3 months will complete a questionnaire to assess gastrointestinal symptoms, which will be based on those used in our previous human Irritable Bowel Syndrome (IBS) trials. Urine will be collected at t=0 (before BP), t=2d (24h after BP), t=8d (1 week after BP) and t=3 months (when recalled to the hospital). Faeces will be collected at the same timepoints except t=2d, instead the first void following BP will be requested. Patients are sent oral BP by post or collect them from the endoscopy unit, and we will exploit this to deliver faecal sample pots. Samples will be provided either at the hospital and immediately frozen, or patients will be asked to freeze and bring with them to their appointment . Later samples (t-8d, t=3 months), will be kept frozen at home then collected by University of Reading staff once both samples have been collected. Upon collection, patients will be provided with the questionnaire (and self-addressed envelope) to allow comparison of their symptoms 2 weeks and 3 months post BP with those reported beforehand (t=0).