Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome – An Update

Abstract

Small intestinal bacterial overgrowth (SIBO) is one manifestation of gut microbiome dysbiosis and is highly prevalent in IBS (Irritable Bowel Syndrome). SIBO can be diagnosed either by a small bowel aspirate culture showing ≥10 3 colony-forming units (CFU) per mL of aspirate, or a positive hydrogen lactulose or glucose breath test. Numerous pathogenic organisms have been shown to be increased in subjects with SIBO and IBS, including but not limited to Enterococcus, Escherichia coli, and Klebsiella. In addition, Methanobrevibacter smithii, the causal organism in a positive methane breath test, has been linked to constipation predominant irritable bowel syndrome (IBS-C). As M. smithii is an archaeon and can overgrow in areas outside of the small intestine, it was recently proposed that the term intestinal methanogen overgrowth (IMO) is more appropriate for the overgrowth of these organisms. Due to gut microbiome dysbiosis, patients with IBS may have increased intestinal permeability, dysmotility, chronic inflammation, autoimmunity, decreased absorption of bile salts, and even altered enteral and central neuronal activity. As a consequence, SIBO and IBS share a myriad of symptoms including abdominal pain, distention, diarrhea, and bloating. Furthermore, gut microbiome dysbiosis may be associated with select neuropsychological symptoms, although more research is needed to confirm this connection. This review will focus on the role of the gut microbiome and SIBO in IBS, as well as novel innovations that may help better characterize intestinal overgrowth and microbial dysbiosis.

Assessment of a 4-Week Starch- and Sucrose-Reduced Diet and Its Effects on Gastrointestinal Symptoms and Inflammatory Parameters among Patients with Irritable Bowel Syndrome

“…Intestinal damage or dysbiosis could contribute to malabsorption and, although organic diseases such as celiac disease and inflammatory bowel disease were ruled out, participants were not investigated for other conditions, such as small-intestinal bacterial overgrowth (SIBO) [ 38 ]. A large meta-analysis of 25 case-control studies concluded prevalence of the condition in as many as 31% of IBS patients [ 38 ]. Dietary manipulation could affect the microbiota and improve SIBO [ 38 , 39 ].…”

“…A large meta-analysis of 25 case-control studies concluded prevalence of the condition in as many as 31% of IBS patients [ 38 ]. Dietary manipulation could affect the microbiota and improve SIBO [ 38 , 39 ]. A previous report demonstrated that dietary interventions for specific, malabsorbed carbohydrates influenced the composition of the gut microbiota [ 11 ].…”

Correlation Between Facial Skin Microbiota and Skin Barriers in a Chinese Female Population with Sensitive Skin

“…It has been reported that intestinal microbiota disorders may promote the development and deterioration of the symptoms of irritable bowel syndrome, 24 and intestinal microbiota may affect the two-way communication between the enteric nervous system and central nervous system. 25 Previous studies have demonstrated that immune system activation and proinflammatory cytokines may indirectly affect skin.…”

Molecular Mechanisms of Microbiota-Mediated Pathology in Irritable Bowel Syndrome

“…Indeed, dysbiosis is often observed in a variety of intestinal disorders including IBS [ 17 , 35 , 37 ]. For example, the small intestinal bacterial overgrowth (SIBO), characterized by the overgrowth of colonic type bacteria, such as Klebsiella, Enterococcus , and Escherichia , is frequently observed in the small intestine of IBS patients [ 38 , 39 ]. SIBO can potentially induce increased gut permeability, low grade inflammation, dysmotility, and decreased absorption of bile salts, and also alter enteric nervous system (ENS) activity [ 38 ].…”