Small Intestinal Bacterial Overgrowth

Purpose of review

Small intestinal bacterial overgrowth (SIBO) is a chronic gastrointestinal disorder wherein excessive and abnormal growth of bacteria in the small bowel generally causes abdominal pain, bloating, and change in bowel habits. Our understanding of the underlying pathology and microbiome changes in SIBO has advanced greatly in the last 20 years in parallel with advances in treatment methods and diagnostics. Here, we review many of the latest findings that describe the pathophysiology of SIBO as well as its risk factors, clinical behavior, diagnosis, and management.

Recent findings

Studies have begun to employ advanced molecular assays to sequence the small bowel microbiome to reveal the changes evident in SIBO. An increase in the abundance of members of the Enterobacteriaceae is the main alteration to the gut microbiome that correlates with SIBO diagnosis and symptom severity, and enhancement of specific gas-producing pathways has been demonstrated in SIBO. Diagnostic methods continue to evolve with novel methods of small bowel aspiration and changes to interpretation of hydrogen breath tests. Elemental diets are the newest treatment modality that offer an exciting alternative to antibiotic therapy.

Summary

The study of SIBO provides valuable insights into the small bowel microbiome, particularly using molecular testing. Exciting changes to our understanding and treatment of SIBO are already in progress. Future work will be able to better elucidate not only the altered microbiology, but also its gold standard of diagnosis, treatment modalities, and secondary prevention.