ABSTRACT
Irritable Bowel Syndrome (IBS) is a functional gastrointestinal (GI) disorder which is essentially characterized by abdominal pain, fl atulence, distension and borborygmi (30). It is the most common chronic GI disorder, which affects 10 to 20% of the general population in Western countries. Diarrhoea or constipation may predominate or alternate (classifi ed as IBS-D, IBS-C or IBS-A, respectively). Although the aetiology of IBS remains poorly characterised, recent reports suggested abnormalities related to the gut-brain axis, the host immune system, gut permeability and dysmobility, the psyche and the gut microbiota (14, 32). The role of the gut microbiota in the occurrence of functional GI disorders has raised high interest in recent years for the following reasons. First, the faecal microbiota of IBS patients differs signifi cantly to that of healthy individuals (5). Second, treatments known to alleviate GI symptoms in IBS patients such as antibiotics, food restriction or probiotics are known to interfere with the gut microbiota (14, 32). Third, the host functions previously described as altered in IBS such as immune activation in a subset of subjects, increase of gut permeability and dysregulated neural function along the gut-brain axis have all been shown to be closely linked to gut microbiota composition or activity (6) (Fig. 1). There is a rapidly growing body of evidence showing that the GI microbiota is directly involved in mood alteration (11), immune homeostasis (12) and tight junction maintenance (13).
