Management of Small Intestinal Bacterial Overgrowth – SIBO

Sep 9, 2019

Tips to tackle a common problem

SIBO (small intestinal bacterial overgrowth) is a relapsing and remitting condition that may affect up to 10-15% of the general population.  The hallmark of SIBO is that the small intestine becomes colonised with normal occurring gut flora.  The small intestine is normally devoid of any bacterial colonisation but changes in the environment within the small bowel can lead to overgrowth of bacteria which can manifest with a myriad symptoms which are the hallmark of SIBO.


Once a patient develops SIBO they can present with a constellation of symptoms including bloating, abdominal discomfort, gas, diarrhoea and fatigue, amongst many others.  For many years patients with SIBO symptoms have been diagnosed and labelled with irritable bowel syndrome. This is predominantly because there is a lack of consensus and clarity internationally regarding the natural history of the disease, the best modality for diagnosing it but also a lack of robust data on the optimum treatment algorithm for these patients.

The small intestine is not normally colonised by bacteria.  In SIBO, bacteria that normally live within the large bowel start to grow within the small bowel.  They feed off small molecule fermentable carbohydrates and sugars that we ingest. The subsequent gas production in SIBO can cause problems with digestion, absorption of food and damaging the membranes in the lining of the small intestine leading to symptoms.

Risk Factors

Several risk factors have been identified for SIBO. Importantly, it can occur in normal individuals, although some people may have anatomical abnormalities such as previous small bowel resection surgery or gastric bypass.  Several medications slow gut motility such as narcotic pain killers and anti-diarrhoeal agents. These can lead to bacterial overgrowth.  A small number of people who take acid suppression medication drugs such as proton pump inhibitors that reduce the amount of acid going into the small bowel might also get bacterial overgrowth, although this remains disputed.  Patients with underlying connective tissue disorders such as fibromyalgia, Ehlers-Danlos syndrome and rheumatoid arthritis may also be more likely to suffer from relapsing symptoms of small intestinal bacterial overgrowth.


The diagnosis of bacterial overgrowth still remains an area of controversy with several different modalities being proposed. At The London Gastroenterology Centre we offer a simple and non-invasive way of testing for it by using a simple breath test.  There is no universally-acceptable gold standard test for SIBO and the use of the lactulose breath test has become extremely common over the past few years.  The purpose of this test is to try and replicate an environment within the small bowel that would occur on a day-to-day basis in patients with small intestinal bacterial overgrowth and then measure the production of gases that are resultantly produced in the small bowel to quantify whether there is indeed SIBO.  Quantification of hydrogen and methane gas in breath samples is the most inexpensive, non-invasive and probably the most widely available test for a diagnosis of bacterial overgrowth within the United Kingdom.  These gases in human breath reflect the metabolism of fermentable carbohydrates in the small bowel.  It is not entirely clear how valuable repeating a breath test weeks after therapy is.


Treatment of SIBO at The London Gastroenterology Centre comprises three strategies. Firstly is to induce remission of SIBO, secondly is to try and maintain remission and prevent SIBO returning and finally and probably as importantly is to treat or modify the underlying cause or predisposing factors that are leading to the development of SIBO.

The treatment of bacterial overgrowth, although controversial, is still predominantly focussed on trying to decrease the numbers and overgrowth of bacteria in the small bowel and antibiotics remain the mainstay of therapy for now.  The choice, dose and duration of antibiotic therapy are still not fully understood as there have been very limited high-quality studies that guide clinicians on which antibiotic to use. In the future, there will be more focus on much more tailored treatments to target specific parts of an individual’s microbiome. These are not yet available. We generally offer Rifaximin, which is one of the most extensively-studied antibiotics in patients with all types of functional bowel disorders.  Studies showit is safe and effective for treating SIBO. It is particularly effective in those with hydrogen over production and diarrhoea and bloating symptoms. The problem in the United Kingdom is that it is only approved for the use of travellers’ diarrhoea but also in patients with liver disease and therefore its use in small intestinal bacterial overgrowth is often problematic, as many hospitals or GP practices will not prescribe it and patients often have to pay for a two week course of antibiotics.  ALternatives include doxycycline which is much cheaper but has less robust scientific evidence to support its use.

m-SIBO – Production of Methane

It must also be noted that when we carry out breath tests to look for SIBO we also look for methane gas production.  There is good evidence that has been presented recently at Digestive Disease Weekly in Chicago 2017, showing that methane overproduction can lead to slow transit and motility of the gut and these patients often do not respond to Rifaximin alone and need a second antibiotic.  Neomycin is a safe antibiotic that has been used in various other disease states and has been shown to improve methane overproduction in patients.  The use of pro-kinetics in this cohort of patients such as a low dose of a drug called prucalopride can supplement the effect of the antibiotics to stimulate gut motility and enhance the efficacy of the treatment.

Herbal Antibiotics

In some patients there is also the option of herbal antibiotics and I see a lot of patients at The London Gastroenterology Centre who want to explore this.  We are happy to discuss and guide patients as to which herbal antibiotics to use as long as they are sourced from a reputable chemist. The options are however very limited.


Maintenance of remission is very important as SIBO is a relapsing disorder in several patients.  In some studies up to one-third of patients will have a relapse of small intestinal bacterial overgrowth and watchful observation is mandatory in patients after induction of remission of SIBO to ensure if there are recurring symptoms that early treatment is instigated.  In my practice at The London Gastroenterology Centre I use the following modalities in preventing SIBO from returning and one of the things a patient should look at is firstly diet.  Limiting fermentable carbohydrates and following a diet such as the low FODMAP diet can ensure that the luminal environment is exposed to low fermentable foods and can ensure that there is a less favourable environment for any residual bacteria to overgrow.  Data have shown that in some patients a low FODMAP diet alone can induce remission in patients with bacterial overgrowth. As importantly the movement and motility of the small bowel needs to be optimised by the use of pro-kinetics.  Prokinetics help stimulate the MMC (migrating motor complex) of the small intestine to prevent recurrence and recolonization of bacteria. I always advise patients that as soon as they have finished their first course of antibiotic treatment we can look at prokinetics.  Again these fall into herbal options such as iberogast drops which can be taken at night or pharmacological treatments such as a low dose of Resolor (prucalopride) at night. I also encourage patients to explore the use of digestive and pancreatic enzymes in trying to optimise the small bowel environment after treatment to prevent SIBO from returning.

Dietary Control of SIBO

In some patients in whom the above measures have not been successful one can look at using more rigorous dietetic exclusion such as the elemental diet.  I have to be honest that this is only reserved for patients with really refractory symptoms despite at least tow to three courses of antibiotics and failure of a trial of a low FODMAP diet.  In the simplest description an elemental diet is a diet that consists of a liquid formula that contains pre-digested carbohydrates, proteins and fats and has been used for many years in the treatment of conditions such as Crohn’s disease.  What the elemental diet means is that the above nutrients are absorbed very quickly through the digestive system, which is helpful in patients with bacterial overgrowth as we do not want food sitting around in the small intestine where it can be used to fuel gas production for the unwanted overgrowth of bacteria.  An elemental diet provides a way to nourish the patient whilst starving off the bacteria.  Implementing the elemental diet is almost always done under the supervision of one of our expert dieticians, and the patients will drink a formula instead of their regular meals for up to two to three weeks depending on the severity of their symptoms and their medical background.  It must also be emphasised that there is not a plethora of high-quality studies on the use of the elemental diet but there are some studies that have shown that in some patients following 14 days of the elemental diet there is an 80% response with negative breath test after treatment.  Clearly there are drawbacks with this and the most important one is that of compliance; it can be extremely difficult to limit one’s dietary intake just to liquids for two weeks.  If you would like to discuss the use of the elemental diet then please contact The London Gastroenterology Centre to make an appointment to discuss further. We can then connect you with one of our dieticians


Finally there has been a lot of interest in the role of probiotics and prebiotics over the past decade and I often get asked by patients as to whether these have a role in the treatment of bacterial overgrowth.  The exact role of probiotics in the management of SIBO remains unclear and needs to be clarified. Certainly anecdotally it makes sense that by replacing unwanted bacteria with good bacteria so to speak will have a beneficial effect on patients.  Nonetheless I do advise caution on the use of probiotics after treatment of bacterial overgrowth as it can in some patients make things slightly worse in the short term.

In summary as you can read in the paragraphs above small intestinal bacterial overgrowth is a common and often stubborn disease to treat.  We have moved away from focusing purely on an antibiotic-focussed treatment of these patients and are now able to offer a variety of different  interventions that I am happy to discuss with patients in clinic.

Make An Appointment

If you would like to make an appointment to be tested for SIBO or discuss management of your SIBO then please contact the team at the London Gastroenterology Centre on the number below.

We are available to see patients daily for private consultations

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