 Alterations in the function and composition of the gut microbiota are increasingly being implicated as potential aetiological factors. Collins et al. One of the strongest indictors for this concept is the significantly increased risk of developing IBS after an episode of acute gastroenteritis. Prospective studies have demonstrated that between 3- 36 of enteric infections lead to new, persistent IBS symptoms. Gwee at al.,Neal et al A number of studies have demonstrated that the diversity, stability and metabolic activity of the gut microbiota are altered in IBS patients compared with healthy individuals Jeffrey et al. Although a distinct microbial signature has not been identified for IBS, several studies have shown a gut microbial composition enriched with Firmicutes together with a reduced abundance of Bacteroides Jeffery et al, Rajilic-Stojanovic et al. 