Treatment of irritable bowel syndrome with probiotics. An etiopathogenic approach at last?

Irritable bowel syndrome (IBS) is the most common functional digestive disorder, and may affect 11-20% of the adult population in industrialized countries. In accordance with Rome III criteria (2006) IBS involves abdominal pain and bowel habit disturbance, which are not explained by structural or biochemical abnormalities. Several hypotheses attempt to account for the pathophysiology of IBS, but the etiology still remains uncertain or obscure, perhaps multifactorial. Abnormalities in colonic microflora have recently been suggested in such patients, as has abnormal small-intestine bacterial overgrowth (SIBO), or in particular a significant reduction in the amount of intraluminal Bifidobacteria or Lactobacilli, with consequences like the production of colonic gas, and motility or sensitivity disturbances of the intestinal tract. The disorder is difficult to treat, and the wide spectrum of non-drug and drug treatments shows our ignorance about the cause of the condition. Newer drugs, both pro- and anti-serotonin, have failed to show long-term efficacy or have been withdrawn due to concerns about harmful effects. Recent research has provided increasing support for the idea that disturbances of intestinal microbiota occur in patients with IBS, and that such abnormalities may contribute to IBS symptoms. Studies in Scandinavian countries in the last ten years emphasize the role of probiotics in the modulation of intestinal microbiota, and as a consequence in the regulation of the motility and hypersensitivity of the digestive tract. Although results between studies are difficult to compare because of differences in study design, probiotic dose, strain, and duration of therapy, some studies show symptom improvement. Lactobacilli are found among the normal bacterial flora of the gastrointestinal tract, and Lactobacillus plantarum (Lp) is one of the species frequently isolated from the human mucosa, which is capable of surviving the low pH of the stomach and duodenum, resisting the effect of bile acids in the upper small intestine when ingested, and temporarily colonizing the gastrointestinal tract by binding to the intestinal and colonic mucosa. Concurrent with colonization by Lp there is a decrease in bacterial groups with gas-producing ability, such as Veillonella spp. and Clostridia spp. Evidence has now accumulated to suggest the efficacy of certain probiotics like Lp299v, which may be capable of bringing about a significant reduction in pain, abdominal distension and flatulence, while increasing health-related quality of life in IBS.