title: Small intestinal bacterial overgrowth as a cause for irritable bowel syndrome: guilty or not guilty?
abstract: OBJECTIVE
  Small intestinal bacterial overgrowth (SIBO) has been proposed as a cause of irritable bowel syndrome (IBS). However, this relationship has been subject to controversy. This review aims to provide a current perspective on the SIBO-IBS hypothesis.
  
  
  RESULTS
  Case-control studies evaluating the prevalence of SIBO in IBS and healthy individuals have shown conflicting results. Moreover, the tests available in routine clinical practice to diagnose SIBO are not valid and lack both sensitivity and specificity. Hence, interpreting the effect of interventions based on these tests is fraught with uncertainty. Furthermore, the SIBO-IBS hypothesis has paved the way to assess antibiotic therapy in nonconstipated IBS, with rifaximin, a nonabsorbable antibiotic, showing modest but significant clinical benefit. However, individuals were not tested for SIBO and the mechanism of action of rifaximin in IBS remains to be elucidated. Preliminary data suggest that rifaximin decreases microbial richness and previous studies have noted antibacterial interventions in IBS to reduce colonic fermentation and improve symptoms. The advent of rapid culture-independent molecular techniques is a promising tool that will seek to clarify and advance our understanding of the gut microbial function.
  
  
  CONCLUSIONS
  The SIBO-IBS hypothesis lacks convincing evidence but remains under scrutiny. The mechanism resulting in symptom improvement after rifaximin treatment in some IBS individuals requires exploration. Novel molecular techniques provide an exciting and challenging opportunity to explore the host-gut microbiota interaction.
authors.affiliation: Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Imran
authors.initials: I
authors.lastname: Aziz
authors.forename: Hans
authors.initials: H
authors.lastname: Törnblom
authors.forename: Magnus
authors.initials: M
authors.lastname: Simrén
mesh_terms: D000890:Anti-Infective Agents / Q000627:therapeutic use; D001765:Blind Loop Syndrome / Q000150:complications* / Q000175:diagnosis / Q000188:drug therapy; D001944:Breath Tests / Q000379:methods; D000069196:Gastrointestinal Microbiome; D006801:Humans; D007421:Intestine, Small / Q000382:microbiology*; D043183:Irritable Bowel Syndrome / Q000382:microbiology*; D012294:Rifamycins / Q000627:therapeutic use; D000078262:Rifaximin
chemical_list: D000890:Anti-Infective Agents; D012294:Rifamycins; D000078262:Rifaximin