Written by Dr Rui Lopes (MD), a physician researcher and medical advisor for OMED Health® which offers breath-based devices, diagnostic and treatment solutions for gastrointestinal diseases.

Approximately 20 per cent of the UK population is thought to suffer from irritable bowel syndrome (IBS).1 Yet, despite recent efforts to raise awareness around gastrointestinal (GI) disease and IBS, few people – including healthcare professionals – have heard about small intestinal bacterial overgrowth (SIBO). SIBO is often an underdiagnosed disease that significantly impacts patients’ quality of life and is thought to affect up 80 per cent of people who fulfill IBS diagnostic criteria.2

While SIBO is recognised in gastroenterology and by those who frequently treat gut-brain axis gastrointestinal disorders, skepticism persists. This often stems from the lack of awareness of compelling research, SIBO’s clinical overlap with other GI conditions and the absence of universally agreed-upon diagnostic and treatment guidelines. Acknowledging both the challenges and the evidence supporting SIBO is the best approach for healthcare professionals. For patients with unexplained gastrointestinal symptoms, considering SIBO as a differential diagnosis, when clinically appropriate, can lead to meaningful relief and improved quality of life for patients.

What is SIBO?

SIBO is a gastrointestinal disease in which bacteria normally found in the colon are seen in excess in the small intestine, which can lead to GI symptoms and, in extreme cases, malabsorptive states.3

The stomach and small intestine have relatively few bacteria due to the acidic environment, presence of digestive enzymes and GI tract motility. When these protective mechanisms are affected, invasive bacterial strains proliferate causing an imbalance in the gut microbiome which in turn can lead to SIBO.3 Several organisms have been identified as frequently responsible for SIBO, such as Escherichia coli, Klebsiella spp and other populations such as Lactobacillus, Streptococci and Bacteroides.4-6

Most patients with SIBO complain of bloating, flatulence, abdominal discomfort, constipation or diarrhea. Physical examination is usually normal, with occasional patients having distended abdomen and palpable bowel loops. Deranged laboratory tests are usually found in severe cases.7,8

The exact prevalence of SIBO is unclear, with studies suggesting it can affect up to 80 per cent of people with IBS and a significant proportion of those with celiac disease, chronic pancreatitis, and post-surgical anatomical changes (such as after a gastric bypass).2

When to consider SIBO diagnosis and what diagnostic tests are available?

The diagnosis of SIBO should be suspected in patients with GI symptoms such as bloating, flatulence, abdominal pain, constipation or diarrhea. Historically, diagnosing SIBO has relied on invasive techniques such as small intestine aspirate and culture, considered the gold standard but rarely used in clinical practice due to inherent limitations.9

Consequently, many healthcare professionals have shifted toward non-invasive techniques. Breath tests are cost-effective, portable and widely available. They are based on the principle that human cells can’t produce hydrogen and methane and, therefore, if these gases can be detected in breath, there must be an alternative source such as the fermentation of a carbohydrate substrate by organisms in the gut, providing indirect but clinically significant evidence of bacterial overgrowth.7

However, while they have transformed SIBO diagnostics, several limitations exist relating to test preparation, standardised protocols and interpretation of results.10 Nonetheless, breath tests remain the most practical and widely accepted way of diagnosing SIBO in clinical practice.

Best treatment options for SIBO

Accurate diagnosis is only the first step. The appropriate management of SIBO can dramatically improve symptoms and overall health. The mainstay of therapy for SIBO includes:

  • Antibiotics: Rifaximin is the most prescribed antibiotic, particularly effective for hydrogen-dominant SIBO.11 For methane-dominant SIBO (or IMO), a combination of rifaximin and neomycin or metronidazole is normally used.12 Alternative combinations of antibiotics can be used as per clinical judgement, with a few randomised control trials to support it.7
  • Diet: The low FODMAP diet can help reduce fermentable foods and starve the o excess bacteria. FODMAPs are short-chain carbohydrates that are poorly absorbed and rapidly fermented gut bacteria. A diet low in FODMAPs improves bloating in patients with irritable bowel syndrome. When properly treated, patients with SIBO experience significant relief from symptoms, improved nutritional status, and enhanced quality of life.

Recurrent ЅIΒO is also frequent after treatment. Studies have shown recurrence rates are as high as 44 per cent in the first nine months after successful treatment.13 Recurrence is more likely in older adults and those with chronic proton pump inhibitor use.

The OMED Health® Breath Analyzer

Breath data and long-term monitoring

Beyond diagnosis, breath can play a pivotal role in monitoring treatment response and recurrence. Advancements in breath analysis are posed to allow a more complete management of GI disease. Post-treatment breath analysis not only helps confirm bacterial eradication through re-test but allows healthcare professionals to adjust therapy or dietary interventions as needed.

The OMED Health Breath Analyzer allows for at-home patient-led tracking of these gas levels, as well as recording their symptoms on the linked mobile app. Hydrogen and methane readings instantly appear for patients and can be shared with healthcare professionals to keep track of progress and prevent recurrence. OMED Health offers a portable, accessible and reliable diagnostic and long-term monitoring option, allowing healthcare professionals to provide more effective, patient-centred care and transform the lives of those affected with SIBO.

References

  1. NICE (2017). Irritable bowel syndrome in adults: diagnosis and management. National Institute for Health and Care Excellence. http://www.nice.org.uk
  2. Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, Vorisek V, Kopacova M. Small intestinal bacterial overgrowth syndrome. World J Gastroenterol. 2010 Jun 28;16(24):2978-90. doi: 10.3748/wjg.v16.i24.2978. PMID: 20572300; PMCID: PMC2890937.
  3. Shah A, Morrison M, Holtmann GJ. Gastroduodenal “Dysbiosis”: a New Clinical Entity. Curr Treat Options Gastroenterol. 2018 Dec;16(4):591-604. doi: 10.1007/s11938-018-0207-x. PMID: 30421297.
  4. Gorbach SL, Plaut AG, Nahas L, Weinstein L, Spanknebel G, Levitan R. Studies of intestinal microflora. II. Microorganisms of the small intestine and their relations to oral and fecal flora. Gastroenterology. 1967 Dec;53(6):856-67. PMID: 4863722.
  5. Walker MM, Talley NJ. Review article: bacteria and pathogenesis of disease in the upper gastrointestinal tract–beyond the era of Helicobacter pylori. Aliment Pharmacol Ther. 2014 Apr;39(8):767-79. doi: 10.1111/apt.12666. Epub 2014 Feb 24. PMID: 24612362.
  6. Khoshini R, Dai SC, Lezcano S, Pimentel M. A systematic review of diagnostic tests for small intestinal bacterial overgrowth. Dig Dis Sci. 2008 Jun;53(6):1443-54. doi: 10.1007/s10620-007-0065-1. PMID: 17990113.
  7. Pimentel M, Saad RJ, Long MD, Rao SSC. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. Am J Gastroenterol. 2020 Feb;115(2):165-178. doi: 10.14309/ajg.0000000000000501. PMID: 32023228.
  8. Bongaerts GP, Tolboom JJ, Naber AH, Sperl WJ, Severijnen RS, Bakkeren JA, Willems JL. Role of bacteria in the pathogenesis of short bowel syndrome-associated D-lactic acidemia. Microb Pathog. 1997 May;22(5):285-93. doi: 10.1006/mpat.1996.0122. PMID: 9160298.
  9. Cangemi DJ, Lacy BE, Wise J. Diagnosing Small Intestinal Bacterial Overgrowth: A Comparison of Lactulose Breath Tests to Small Bowel Aspirates. Dig Dis Sci. 2021 Jun;66(6):2042-2050. doi: 10.1007/s10620-020-06484-z. Epub 2020 Jul 17. PMID: 32681227.
  10. Riordan SM, McIver CJ, Walker BM, Duncombe VM, Bolin TD, Thomas MC. The lactulose breath hydrogen test and small intestinal bacterial overgrowth. Am J Gastroenterol. 1996 Sep;91(9):1795-803. PMID: 8792701.
  11. Wang J, Zhang L, Hou X. Efficacy of rifaximin in treating with small intestine bacterial overgrowth: a systematic review and meta-analysis. Expert Rev Gastroenterol Hepatol. 2021 Dec;15(12):1385-1399. doi: 10.1080/17474124.2021.2005579. Epub 2021 Nov 26. PMID: 34767484.
  12. Pimentel M, Chang C, Chua KS, Mirocha J, DiBaise J, Rao S, Amichai M. Antibiotic treatment of constipation-predominant irritable bowel syndrome. Dig Dis Sci. 2014 Jun;59(6):1278-85. doi: 10.1007/s10620-014-3157-8. Epub 2014 May 1. PMID: 24788320.
  13. Lauritano EC, Gabrielli M, Scarpellini E, Lupascu A, Novi M, Sottili S, Vitale G, Cesario V, Serricchio M, Cammarota G, Gasbarrini G, Gasbarrini A. Small intestinal bacterial overgrowth recurrence after antibiotic therapy. Am J Gastroenterol. 2008 Aug;103(8):2031-5. doi: 10.1111/j.1572-0241.2008.02030.x. PMID: 18802998.

Dr Rui Lopes is a medical advisor to Cambridge-based OMED Health® supporting their mission to raise awareness of SIBO and empower healthcare professionals to make an accurate diagnosis of this common GI disease. The company is a pioneer in breath testing technology to detect levels of hydrogen and methane in the breath to support the diagnosis of SIBO – a technology that is now starting to be more widely used in NHS trusts. They have also produced several free resources for patients including eBooks on the topics of SIBO and IBS as well as educational blogs.