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 usually diagnosed via a Lactulose breath test. Sometimes it is diagnosed using a bacterial culture. But this is rare due to the difficulty and cost of retrieving a sample from the small intestine. SIBO cannot be diagnosed via stool testing.

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
Any antibiotic that is active in the small intestine may potentially affect the bacterial flora and therefore SIBO. However, certain antibiotics are used preferentially when treatment is explicitly targeting SIBO. These antibiotics may be synthetic or herbal, though synthetic antibiotics appears to be used most often.

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

Herbal

 * Oregano
 * Allicin

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.

Increasing Stomach Acid
In cases where SIBO is caused by low stomach acid, treatment may include dietary supplements that increase stomach acid, such as Betaine Hydrocloride.

Learn more

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