Everything You Need to Know About SIBO: From Diagnosis to Treatment

The Small Intestinal Bacterial Overgrowth (SIBO) syndrome was identified several decades ago, but it has recently gained increasing attention due to advances in understanding the intestinal microbiome and its importance in human health and disease.

The microbiota of the small intestine is less abundant and diverse compared to that of the large intestine. This is due to high peristalsis, constant mucosal renewal, and the presence of bile salts and pancreatic juices, which hinder bacterial colonization. Any disruption in these factors can lead to bacterial overgrowth.

It is estimated that between 2.5% and 22% of the population suffers from SIBO. However, these numbers are underestimated due to asymptomatic cases and nonspecific gastrointestinal symptoms, which can be caused by various factors.

Thus, the true prevalence of the condition remains unknown. It is known, however, that the recurrence of the disease increases with age and in individuals with pre-existing comorbidities such as irritable bowel syndrome, diabetes, liver cirrhosis, and extrahepatic portal vein obstruction. (1). Therefore, it is of utmost importance to accurately diagnose SIBO.

What is Bacterial Overgrowth?

SIBO is a gastrointestinal condition characterized by an imbalance in microbial colonization between the colon and the small intestine. In healthy individuals, there are few microorganisms colonizing the small intestine, whereas those with SIBO show excessive bacterial growth in the proximal portion of the small intestine.

This condition causes alterations in intestinal functions, such as poor absorption, where nutrients not absorbed in the small intestine are fermented by bacteria, resulting in excessive gas production. This can lead to nutritional deficiencies and affect quality of life (2).

The general population’s diet is predominantly rich in carbohydrates, which, when fermented, can generate short-chain fatty acids and gases such as carbon dioxide (CO2), hydrogen (H2), and methane (CH4) (2,3).

Bacterial overgrowth can occur due to overload, insufficiency, or absence of protective mechanisms that ensure intestinal microbiota homeostasis and prevent excessive bacterial colonization. Among these defense mechanisms, notable ones include the production of antimicrobial substances, gastrointestinal motility, and the anatomy of the gastrointestinal tract (4).

Under normal conditions, the production of antimicrobial substances like hydrochloric acid maintains an acidic pH, reducing the likelihood of pathogenic microorganism growth. However, this production can be insufficient in cases of atrophic gastritis, prolonged use of proton pump inhibitors, or gastric resection.

The secretion of pancreatic enzymes, essential for proper digestion, can be affected in chronic pancreatitis or cystic fibrosis. Additionally, mucosal immunity may be compromised in immunocompromised patients or those with inadequate secretion of IgA, making defense against excessive bacterial colonization difficult.

Gastrointestinal motility must be adequate for nutrient absorption and to prevent microbial proliferation. However, certain disorders can affect this motility, such as intestinal obstruction, neuropathies secondary to diabetes, and Parkinson’s disease.

Additionally, the anatomy of the gastrointestinal tract plays a crucial role in regulating intestinal microbiota and can be altered due to Crohn’s disease, radiotherapy, or surgical interventions (such as gastrojejunostomy, colectomy, or resection of the ileocecal valve) (4).

What are the Symptoms of SIBO?

The signs and symptoms are a consequence of intestinal dysfunctions and therefore are often nonspecific. However, they are associated with gastrointestinal symptoms such as (5):

• Diarrhea or constipation;
• Gas;
• Flatulence;
• Belching;
• Abdominal bloating and distension;
• Nausea;
• Abdominal pain.

Some patients may also experience fatigue, lack of concentration, anxiety, and in more severe cases, they may present steatorrhea, weight loss, anemia, and deficiency of fat-soluble vitamins such as B12 and vitamin D.

What is the relationship between SIBO and gastrointestinal diseases?

There is a correlation between SIBO and irritable bowel syndrome (IBS), chronic pancreatitis, cystic fibrosis, celiac disease, Crohn’s disease, and other conditions that can coexist due to a disorder in the intestinal microbiota (1, 6).

• Irritable Bowel Syndrome (IBS): Studies suggest that 78% of people with IBS also suffer from SIBO, making it difficult to clinically differentiate between both conditions (7). Intestinal dysbiosis in SIBO can contribute to the pathogenesis of IBS, characterized by a decrease in butyrate-producing bacteria and an increase in GLP-1 production, which reduces intestinal motility and promotes bacterial overgrowth in the small intestine (4).

• Chronic Pancreatitis: Inflammation in the pancreas destroys acinar cells, affecting the secretion of essential pancreatic enzymes for digestion and defense against microorganisms. The resulting malabsorption creates a conducive environment for SIBO. Approximately 38.6% of patients with chronic pancreatitis have SIBO (8).

• Cystic Fibrosis: Alterations in chloride and bicarbonate transport in intestinal cells reduce intestinal fluidity and motility, promoting inflammation and dysbiosis. Studies indicate that between 30% and 40% of people with cystic fibrosis suffer from SIBO (9).

• Celiac Disease: The prevalence of SIBO in celiac disease is estimated to be around 20%, potentially higher when symptoms persist after a gluten-free diet (10). Celiac disease damages the intestinal epithelium and disrupts intestinal motility, reducing physiological antimicrobial defense and resulting in bacterial overgrowth (11).

• Crohn’s Disease: Approximately 30% of adults with Crohn’s disease have SIBO, often due to gastrointestinal surgeries, especially ileocecal resection, dysmotility, strictures, or fistulas. Individuals with fibrostenotic Crohn’s disease are 7.5 times more likely to develop SIBO due to intestinal narrowing and prolonged transit time, which promotes bacterial proliferation (12).

Also consult about Intestinal Permeability, the root of many problems.

What are the indications for the SIBO test?

The SIBO test is an important option to consider in the presence of any undiagnosed gastrointestinal manifestations such as:

• Abdominal distension;
• Excessive flatulence;
• Recurrent abdominal pain;
• Chronic diarrhea or constipation;
• Feeling bloated after meals.

Presence of pre-existing diseases that do not respond to treatment or that present intestinal malabsorption such as:

• Irritable bowel syndrome;
• Celiac disease;
• Crohn’s disease;
• Cystic fibrosis;
• Chronic pancreatitis;
• Dysfunction of the lower esophageal sphincter;
• Individuals who have undergone abdominal surgeries.

How can SIBO be diagnosed?

The diagnosis of SIBO is usually performed through microbiological culture of the small intestine aspirate, obtained via endoscopy, considered the gold standard. However, this procedure is invasive and the sample can be contaminated (12).

In culture, bacteria such as Streptococcus spp., Staphylococcus spp., Escherichia coli, Klebsiella, Proteus, Bacteroides, and Lactobacillus are often detected (13).

Although considered the most accurate method, microbiological culture has significant limitations. Apart from being time-consuming, invasive, and relatively expensive, standardized techniques that completely eliminate the risk of contamination are lacking.

With advances in science, innovative tests have been developed for detecting microorganisms through gas production, such as the breath test. This method allows SIBO analysis from a simple sample of air exhaled by the individual, using a safe and non-invasive technique. It is based on the principle that human cells cannot produce hydrogen and methane.

What is the SIBO diagnostic test offered by SYNLAB?

In this context, SYNLAB offers the hydrogen and methane breath test to detect bacterial overgrowth, evaluating the production of carbon dioxide (CO2), hydrogen (H2), and methane (CH4). The test involves eight collections of exhaled air, allowing for precise identification of bacterial overgrowth.

The test begins with ingestion of a carbohydrate, such as lactulose. Fermentation of this by the microbiota in the small intestine can result in the production of hydrogen and/or methane, depending on the microorganisms involved. The presence of methane is associated with overgrowth of archaea, whereas hydrogen is associated with bacterial overgrowth (11). The gases produced diffuse into the bloodstream and are excreted through breathing.

The need for eight tubes is crucial to assess the fermentation process over time. Collection is done every 30 minutes after ingestion of the carbohydrate, starting before ingestion and continuing through to the eighth tube after 210 minutes. This allows for the creation of a curve of gases expelled over time.

The SIBO test analyzes gases using Gas Chromatography methodology (Quintron Breathtracker SC, with CO₂ dilution correction factor). This technique separates and analyzes volatile and semi-volatile compounds present in exhaled air using a stationary phase and a mobile phase to determine analyte retention times and allow for gas separation.

SYNLAB utilizes the Quintron Breathtracker SC, a device that facilitates analysis and is capable of detecting small quantities of respiratory gases. Results are measured and displayed in parts per million (ppm) for H2 and CH4, and in percentage (%) for CO₂. Additionally, it includes an additional function to detect and correct sample contamination based on CO₂ measurements.

The non-invasive collection method, combined with the advanced technology of the test provided by SYNLAB, allows for precise diagnosis essential for guiding appropriate treatment.

It’s important to note that the SIBO test result should be interpreted by the requesting physician within the patient’s clinical context, ensuring recommendations for suitable and personalized treatment.

How to treat SIBO?

SIBO treatment aims primarily to eradicate bacterial overgrowth to alleviate symptoms. It is primarily based on the use of antibiotics, which may be associated with a specific diet and the use of probiotics.

However, some patients may remain symptomatic due to underlying conditions or bacteria resistant to antibiotics.

Due to the development of bacterial resistance, adverse reactions, and increased opportunistic infections, a cautious approach is required. Antibiotics are used to eliminate most bacteria without compromising intestinal flora.

However, SIBO often recurs after antibiotic treatment (14). There are treatment options with specific medications that do not induce bacterial resistance and can be used again to reduce recurrence (1).

Additionally, a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet can be implemented, aiming to reduce the energy source for bacterial proliferation and fermentation, thereby reducing bacterial growth and gas production.

However, the FODMAP diet should be completely eliminated from the diet of SIBO patients for a maximum of six weeks, and if it is not effective, it should not be used again in the future (1). Therefore, it is important to follow up with a specialized doctor.

Probiotics are also an option, consisting of beneficial live microorganisms that compete for nutrients and adhere to the intestine, inhibiting the growth of other microorganisms. They can produce antimicrobial substances and numerous metabolites, such as lactic acid, which hinder microbial proliferation (1).

On the other hand, it should be considered that probiotics may inadvertently colonize the small intestine, potentially exacerbating symptoms in some cases, depending on the strain used in treatment (15). Therefore, probiotic therapy should be carefully evaluated on an individual basis, as it may yield varying results among patients. Specialized medical follow-up is essential to adjust treatment according to the patient’s response and specific clinical needs.

Get to Know the SYNLAB Group, a Leader in Medical Diagnostic Services!

Performing precise and up-to-date examinations is essential for obtaining more accurate diagnoses and better directing treatments. SYNLAB is here to help.

We offer diagnostic solutions with strict quality control to the companies, patients, and physicians we serve. With over 10 years of operation in Brazil, we operate in 36 countries across three continents and are leaders in service provision in Europe.

Contact the SYNLAB team to learn about the available tests.

References

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2. Pimentel, Mark MD, FRCP(C), FACG; Saad, Richard J. MD, FACG; Long, Millie D. MD, MPH, FACG (metodologista GRADE); Rao, Satish SC MD, PhD, FRCP, FACG. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. The American Journal of Gastroenterology 115(2):p 165-178, 2020.
3. Gasbarrini A, Corazza GR, Gasbarrini G, et al. Methodology and Indications of H2-Breath Testing in Gastrointestinal Diseases: the Rome Consensus Conference. Aliment Pharmacol Ther 2009;29(Suplemento 1):1–49.
4. Dos Santos, D. L. D. C. (2023). O papel da microbiota na Síndrome do Intestino Irritável(Doctoral dissertation, UNIVERSIDADE DE COIMBRA).
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6. Ghoshal, U. C., Srivastava, D., Ghoshal, U., Misra, A.. Breath tests in the diagnosis of small intestinal bacterial overgrowth in patients with irritable bowel syndrome in comparison with quantitative upper gut aspirate culture. European journal of gastroenterology & hepatology, 26(7), 753–760, 2014.
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9. Dorsey, J., & Gonska, T. (2017). Bacterial overgrowth, dysbiosis, inflammation, and dysmotility in the Cystic Fibrosis intestine. Journal of cystic fibrosis : official journal of the European Cystic Fibrosis Society, 16 Suppl 2, S14–S23.
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13. Erdogan A, Rao SS, Gulley D, et al. Small intestinal bacterial overgrowth: Duodenal aspiration vs glucose breath test. Neurogastroenterol Motil 2015;27:481–9.
14. Banaszak M, Górna I, Woźniak D, Przysławski J, Drzymała-Czyż S. Association between Gut Dysbiosis and the Occurrence of SIBO, LIBO, SIFO and IMO. Microorganisms. 2023; 11(3):573.
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