By Jun Kim Ph.D.
Irritable bowel syndrome (IBS) affects millions of people worldwide. It is a chronic disorder that affects the colon and causes cramping, abdominal pain, bloating, gas, diarrhea, and constipation. Unlike inflammatory bowel disease (IBD), IBS does not produce the destructive inflammation and usually show no sign of disease or abnormalities. Because much is still unknown about IBS currently there is no cure and only the symptoms can be treated. Over the past decade, studies have been suggesting new mechanisms of IBS. Some of these studies suggest small intestinal bacterial overgrowth, or SIBO, as a potential cause of IBS.
In 1977, Vantrappen et al. discovered that patients with bacterial overgrowth had abnormal motility in the intestines . Further studies confirmed the finding in IBS patients , and IBS symptoms decreased when the bacterial overgrowth was controlled with antibiotics. For example, a study of 202 patients with IBS found that 78% of the patients with IBS also had bacterial overgrowth. When treated with antibiotics, 53% of the patients with bacterial overgrowth reported improvement in their IBS symptoms . In another study, 84% of 111 patients with IBS had bacterial overgrowth, and again, treatment with antibiotic led to a reduction in IBS symptoms . Despite the variability in the percentage of IBS patients having bacterial overgrowth, for those who do effective treatment with antibiotics has been confirmed in different studies [5,6].
A number of studies have been conducted to evaluate the benefits of probiotics on IBS and demonstrated symptom improvement [7–10]. Experimental studies have shown that probiotics can compete with pathogens, produce bacteriocins, inhibit bacterial translocation, enhance mucosal barrier function, and regulate immune system [11–18]. For SIBO, a direct evidence of benefit comes from studies of probiotics in experimental models of translocation of gastrointestinal bacteria into other sites in the body. For example, Adawi et al. showed that Lactobacillus plantarum reduced the total number of bacteria translocated to mesenteric lymph nodes, portal blood, and the liver , and others demonstrated similar results in other animal models [20,21]. Human studies also suggest that that L plantarum may either prevent or delay symptom recurrence after antibiotic therapy . One study showed that both L. casei and L. acidophilus proved effective for bacterial overgrowth-related chronic diarrhea .
With different probiotic dose and strain, the studies with probiotics are difficult to be compared. In general, probiotics appear to possess a number of properties that could be of benefit in SIBO. Their use as a therapy, however, requires validation by well-conducted clinical trials.
Disclaimer: The above article is sponsored by Thyrve, the world’s first Gut Health Program that incorporates microbiome testing and personalized probiotics to ensure a healthier gut, happier life, and a brighter future.
 Vantrappen G, Janssens J, Hellemans J, Ghoos Y: The interdigestive motor complex of normal subjects and patients with bacterial overgrowth of the small intestine. J Clin Invest 1977, 59:1158–1166.
 Pimentel M, Soffer EE, Chow EJ, Kong Y, Lin HC: Lower frequency of MMC is found in IBS subjects with abnormal lactulose breath test, suggesting bacterial overgrowth. Digestive Diseases and Sciences 2002, 47:2639–2643.
 Pimentel M, Chow EJ, Lin HC: Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. American Journal of Gastroenterology 2000, 95:3503–3506.
 Pimentel M, Chow EJ, Lin HC: Normalization of lactulose breath testing correlates with symptom improvement in irritable bowel syndrome: A double-blind, randomized, placebo-controlled study. American Journal of Gastroenterology 2003, 98:412–419.
Peralta S, Cottone C, Doveri T, Almasio PL, Craxi A: Small intestine bacterial overgrowth and irritable bowel syndrome-related symptoms: Experience with Rifaximin. World Journal of Gastroenterology 2009, 15:2628–2631.
 Majewski M, Reddymasu SC, Sostarich S, Foran P, McCallum RW: Efficacy of rifaximin, a nonabsorbed oral antibiotic, in the treatment of small intestinal bacterial overgrowth. American Journal of the Medical Sciences 2007, 333:266–270.
 Niedzielin K, Kordecki H, Birkenfeld B: A controlled, double-blind, randomized study on the efficacy of Lactobacillus plantarum 299V in patients with irritable bowel syndrome. European Journal of Gastroenterology & Hepatology 2001, 13:1143–1147.
 Halpern GM, Prindiville T, Blankenburg M, Hsia T, Gershwin ME: Treatment of irritable bowel syndrome with Lacteol Fort: a randomized, double-blind, cross-over trial. Am J Gastroenterol 1996, 91:1579–1585.
 O’Sullivan MA, O’Morain CA: Bacterial supplementation in the irritable bowel syndrome. A randomised double-blind placebo-controlled crossover study. Dig Liver Dis 2000, 32:294–301.
 Nobaek S, Johansson ML, Molin G, Ahrne S, Jeppsson B: Alteration of intestinal microflora is associated with reduction in abdominal bloating and pain in patients with irritable bowel syndrome. American Journal of Gastroenterology 2000, 95:1231–1238.
 Shanahan F: Probiotics: A perspective on problems and pitfalls. Scandinavian Journal of Gastroenterology 2003, 38:34–36.
 Castagliuolo I, Riegler MF, Valenick L, LaMont JT, Pothoulakis C: Saccharomyces boulardii protease inhibits the effects of Clostridium difficile toxins A and B in human colonic mucosa. Infect Immun 1999, 67:302–307.
 Madsen K, Cornish A, Soper P, McKaigney C, Jijon H, Yachimec C, Doyle J, Jewell L, De Simone C: Probiotic bacteria enhance murine and human intestinal epithelial barrier function. Gastroenterology 2001, 121:580–591.
 Resta-Lenert S, Barrett KE: Live probiotics protect intestinal epithelial cells from the effects of infection with enteroinvasive Escherichia coli (EIEC). Gut 2003, 52:988–997.
 Akhtar M, Watson JL, Nazli A, McKay DM: Bacterial DNA evokes epithelial IL-8 production by a MAPK- dependent, NF-kappaB-independent pathway. FASEB J 2003, 17:1319–1321.
 McCarthy J, O’Mahony L, O’Callaghan L, Sheil B, Vaughan EE, Fitzsimons N, Fitzgibbon J, O’Sullivan GC, Kiely B, Collins JK, et al.: Double blind, placebo controlled trial of two probiotic strains in interleukin 10 knockout mice and mechanistic link with cytokine balance. Gut 2003, 52:975–980.
 Rachmilewitz D, Katakura K, Karmeli F, Hayashi T, Reinus C, Rudensky B, Akira S, Takeda K, Lee J, Takabayashi K, et al.: Toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis. Gastroenterology 2004, 126:520–528.
 Jijon H, Backer J, Diaz H, Yeung H, Thiel D, McKaigney C, De Simone C, Madsen K: DNA from probiotic bacteria modulates murine and human epithelial and immune function. Gastroenterology 2004, 126:1358–1373.
 Adawi D, Molin G, Jeppsson B: Inhibition of nitric oxide production and the effects of arginine and Lactobacillus administration in an acute liver injury model. Ann Surg 1998, 228:748–755.
 Mao Y, Nobaek S, Kasravi B, Adawi D, Stenram U, Molin G, Jeppsson B: The effects of Lactobacillus strains and oat fiber on methotrexate-induced enterocolitis in rats. Gastroenterology 1996, 111:334-344.
 Eizaguirre I, Urkia NG, Asensio AB, Zubillaga I, Zubillaga P, Vidales C, Garcia-Arenzana JM, Aldazabal P: Probiotic supplementation reduces the risk of bacterial translocation in experimental short bowel syndrome. J Pediatr Surg 2002, 37:699–702.
 Young RJ, Vanderhoof JA: Probiotic therapy in children with short bowel syndrome and bacterial overgrowth. Gastroenterology 1997, 112:A916-A916.
 Gaon D, Garmendia C, Murrielo NO, de Cucco Games A, Cerchio A, Quintas R, Gonzalez SN, Oliver G: Effect of Lactobacillus strains (L. casei and L. Acidophillus Strains cerela) on bacterial overgrowth-related chronic diarrhea. Medicina (B Aires) 2002, 62:159–163.