Jejunal Fermenters – Causes, Symptoms & Treatment

What Are Jejunal Fermenters?

Jejunal fermenters are microorganisms – predominantly bacteria – that colonize the jejunum, the middle section of the small intestine, and ferment nutrients such as carbohydrates in this location. Under normal conditions, microbial fermentation occurs primarily in the large intestine (colon). When bacteria carry out fermentation processes in the small intestine, this is referred to as pathological bacterial overgrowth or aberrant fermentation in the jejunum.

Causes

Jejunal fermenters typically arise as part of a condition known as Small Intestinal Bacterial Overgrowth (SIBO). Common contributing factors include:

• Reduced intestinal motility (slow gut movement), as seen in diabetes mellitus or hypothyroidism
• Anatomical changes following gastrointestinal surgery
• Decreased gastric acid production (e.g., due to long-term use of proton pump inhibitors)
• Conditions such as Crohn's disease, scleroderma, or irritable bowel syndrome
• Immune deficiency or malnutrition
• Dysfunction of the ileocecal valve, which normally prevents colonic bacteria from entering the small intestine

Symptoms

Because jejunal fermenters break down carbohydrates in the small intestine, they produce fermentation gases (mainly hydrogen, methane, and carbon dioxide) as well as organic acids. Typical symptoms include:

• Significant bloating and a feeling of fullness shortly after eating
• Abdominal cramps and pain
• Diarrhea or constipation, often alternating
• Nausea
• Signs of nutritional deficiency due to impaired nutrient absorption (malabsorption), such as vitamin B12 deficiency or iron deficiency
• Unintentional weight loss and fatigue

Diagnosis

Diagnosing small intestinal bacterial overgrowth involving jejunal fermenters is typically done through:

• Breath tests: The hydrogen breath test (H2 breath test) or methane breath test measures gas production after ingestion of a sugar solution (lactulose or glucose). An early rise in gas levels indicates fermentation occurring in the small intestine.
• Jejunal aspiration: Collection and culture of fluid directly from the jejunum via endoscopy – considered the gold standard, though technically demanding.
• Blood tests to assess nutritional deficiencies (vitamin B12, folate, iron)
• Stool tests and imaging to rule out other conditions

Treatment

Treatment is tailored to the underlying cause and generally involves a combination of approaches:

Antibiotic Therapy

To reduce bacterial overgrowth, specific antibiotics are used. Rifaximin is a non-absorbable antibiotic that acts locally in the small intestine and is often considered the first-line treatment. Other antibiotics such as metronidazole or neomycin may also be used.

Dietary Modification

A low-FODMAP diet (reduction of certain fermentable carbohydrates) can significantly relieve symptoms by limiting the substrate available to jejunal fermenters.

Probiotics

Certain probiotic strains may help restore a healthy microbial balance in the gut, although the scientific evidence in this area is still developing.

Treatment of the Underlying Condition

Addressing the root cause (e.g., optimizing diabetes management, discontinuing proton pump inhibitors, or surgical correction of anatomical abnormalities) is essential for long-term prevention of recurrence.

Nutritional Supplementation

Existing deficiencies (vitamin B12, iron, fat-soluble vitamins) are specifically corrected through targeted supplementation.

References

1. Bures J. et al. - Small intestinal bacterial overgrowth syndrome. World Journal of Gastroenterology. 2010;16(24):2978-2990.
2. Ghoshal UC, Shukla R, Ghoshal U. - Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut and Liver. 2017;11(2):196-208.
3. Gasbarrini A. et al. - Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference. Alimentary Pharmacology and Therapeutics. 2009;29(Suppl 1):1-49.