Small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) is an excessive population of bacteria in the small intestine. Unlike the large intestine, which is has a very high population of bacteria, the small intestine ordinarily has a very low population of bacteria in healthy people. SIBO is highly prevalent in ME/CFS patients, for whom it appears to cause or worsen symptoms. Treatment often improves ME/CFS symptoms.

Prevalence
The rate of a positive lactulose test is low in healthy adults (0 to 20%).

Comorbidities
Anecdotal reports suggest a high prevalence of SIBO among CFS patients. One study found 77% of CFS patients had SIBO and eradication lead to decrease in symptoms. Patients with CFS have alterations in microbiota, including lower levels of bifidobacteria and SIBO.

Several studies have shown that up to 84% of patients with irritable bowel syndrome have SIBO and that symptoms improve after treatment, while others fail to replicate these results.

One study found that a 100% of fibromyalgia patients tested positive to a lactulose breath test, indicating SIBO, and that the degree of abnormality on the breath test correlated with the amount of pain reported.

Risk factors

 * Bowel resection
 * Bariatric surgery
 * Disordered motility
 * Disorders of the immune system
 * IgA deficiency
 * Low stomach acid
 * Proton pump inhibitors
 * Immunosuppressants
 * Recurrent antibiotic use
 * Hypothyroidism
 * T4-only thyroid hormone replacement
 * Gastroparesis
 * Celiac disease
 * Crohn's disease
 * Pancreatitis
 * Renal failure
 * Old age

Diagnosis
SIBO is most commonly diagnosed via a breath test, and rarely diagnosed via bacterial culture. SIBO cannot be diagnosed via stool testing.

Breath Testing
Breath Testing is an indirect method of measuring the population and location of bacteria in the digestive tract. It works by detecting gasses produced by bacteria as they metabolize food that is passing through the digestive tract.

Test equipment may measure the concentration (in PPM) of Hydrogen gas, Methane gas, or both. Measuring the concentration of both gasses is ideal to ensure that both aerobic and anaerobic bacteria are detected. However, testing may be limited to measuring only hydrogen due to available equipment and/or cost considerations.

Diagnosis of SIBO via breath testing is controversial due to the species-dependent nature of breath tests and the lack of an agreed threshold for a positive test.

Procedure
The test is preceded by a 24 hour preparation period, which includes a limited diet and a period of fasting. Baseline gas levels are measured from the patients breath at the beginning of the test. Then a certain amount of food is administered - typically a small volume of Lactulose solution. Measurement of the patient's breath gas levels is repeated periodically - typically every 15 to 30 minutes - for a few hours. SIBO may be indicated if one or both of the following criteria are met: Testing may be done in-office or at home using portable, possibly even handheld, breath testing equipment. Alternatively, breath samples may be collected using a kit then shipped to a remote lab where equipment is used for analysis.
 * Gas level rises above a certain threshold within a certain timeframe. (The idea is that food travels through the small intestine before reaching the large intestine.  Thus, an early rise means that bacteria must be present in the small intestine.)
 * Gas level plot shows a double peak. (The idea is that this indicates two clusters of bacteria - one in the small intestine, and one in the large intestine.)

Bacterial Culture
This requires retrieving a bacteria sample from the small intestine via intubation. This procedure is rarely used, owing to the difficulty and cost.

Pathophysiology
SIBO appears to caused increased intestinal permeability, also known as Leaky Gut. It is believed that this enables lipopolysaccharides from bacteria, food particles, and other undesirable substances to enter the blood stream, ultimately leading to an inflammatory response.

Bacteria commonly implicated in SIBO include Escherichia coli, Streptococcus, Lactobacillus, Bacteroides and Enterococcus. Higher levels of Enterococcus and Stretptococcus have been found in ME/CFS patients.

Health complications
The symptoms of SIBO can vary greatly depending on the severity and the species of bacteria populating the small intestine. Symptoms include bloating, abdominal distension, abdominal pain or discomfort, diarrhea, fatigue, weakness, and brain fog.

It causes increased permeability of the small intestine. It can cause malabsorption of nutrients including iron and Vitamin B12, resulting in microcytic anemia or megaloblastic anemia.

Nutritional deficiencies
Vitamin B12 malabsorption may be caused by competitive uptake of B12 by bacteria in the small intestine. It can also cause excess folic acid due to synthesis by bacteria in the small bowel.

In severe cases, malabsorption of fat-soluble vitamins (A,D,E and K) due to the deconjugation of bile salts can cause neuropathies and immune dysfunction.

SIBO can also cause carbohydrate and protein malabsorption.

Treatment
Treatment generally involves some combination of antibiotics, dietary changes, pro-kinetic agents, and probiotics. Treatment via antibiotics is most common.

Antibiotics
Both synthetic and herbal may be used. Use of synthetic antibiotics appears to be more common.

Synthetic
Rifxaimin is the most commonly used antibiotic used for SIBO treatment. It is effective on hydrogen producing bacteria, but not methane producing bacteria. Only a small percentage of the drug is absorbed by the body, and its activity is mostly limited to the small intestine.

Neomycin is sometimes given in addition to Rifaximin when methane-producing bacteria are present. However, one study comparing two herbal formulations to standard treatment found herbs to be as or more effect as antibiotics for eradicating SIBO.

Metronidazole has also been used.

Herbal
Oil of Oregano has been studied.

Diet
Diets have been used and/or shown to be helpful in treating or controlling SIBO include:
 * GAPS Diet
 * Low FODMAP Diet
 * Specific Carbohydrate Diet
 * Elemental Diet

Pro-kinetic Agents
Experts also recommend the use of prokinetic drugs or herbs for those for whom dysmotility is an issue. These agents include:
 * Low Dose Naltrexone (LDN)

Probiotics
The role of probiotics in treatment is controversial.

One school of thought is that SIBO is not due to a "bad" bacteria, but rather a simple overgrowth of ordinary / healthy bacteria. Therefore, it would follow that probiotics would be counterproductive to treating and managing SIBO.

Another school of thought is that SIBO is caused or worsened by the presence of a "bad" bacteria, or a bad mix of bacteria. Therefore, it would follow that probiotics that increase the level of "good" bacteria, or promote a healthier mix of bacteria, would be helpful in treating or managing SIBO. Lactobacillus casei has been found to improve breath hydrogen scores after six weeks of treatment. There is also evidence for VSL in the treatment of SIBO. However, some probiotics may exacerbate SIBO, in particular those containing D-Lactate producing strains.

Learn more

 * June 29, 2018 - "SIBO Treatment with Herbs Is as Effective as Antibiotics". University Health News