Does a glucose‐based hydrogen and methane breath test detect bacterial overgrowth in the jejunum?

• Published in: Neurogastroenterology and motility Vol. 30; no. 11; pp. e13350 - n/a
• Main Authors: Sundin, O. H., Mendoza‐Ladd, A., Morales, E., Fagan, B. M., Zeng, M., Diaz‐Arévalo, D., Ordoñez, J., McCallum, R. W.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-11-2018
• Subjects: Bacteria; bacterial overgrowth; Breath tests; Cell culture; Colonies; Deoxyribonucleic acid; DNA; Dysbacteriosis; Fermentation; Genomes; Glucose; glucose breath test; Hydrogen; Intestine; Jejunum; Methane; quantitative PCR; rRNA 16S; SIBO; Surgery; jejunum; SIBO; glucose breath test; quantitative PCR; bacterial overgrowth
• ISSN: 1350-1925; 1365-2982
• DOI: 10.1111/nmo.13350

Background
Direct diagnosis of small intestinal bacterial overgrowth (SIBO) requires the collection and culture of fluid from the jejunal lumen, with a finding of over 105 viable bacteria per mL. More often, SIBO is diagnosed indirectly, using a non‐invasive test of the exhaled hydrogen and methane generated by microbial fermentation when ingested glucose reaches the jejunum. Our objective was to determine how well this breath test detects chronic overgrowth of jejunal bacteria that is unrelated to gastrointestinal surgery.
Methods
Eighteen patients reporting symptoms consistent with SIBO received a glucose breath test. On a later day, the jejunal lumen was sampled via aspiration during enteroscopy. Jejunal aspirates were cultured on aerobic and anaerobic media. DNA was extracted from the same samples and analyzed by quantitative pan‐bacterial PCR amplification of 16S ribosomal rRNA genes, which provided a culture‐independent bacterial cell count.
Key Results
Combined bacterial colony counts ranged from 5.7 x 103 to 7.9 x 106 CFU/mL. DNA‐based yields ranged from 1.5 x 105 to 3.1 x 107 bacterial genomes per mL. Microbial viability ranged from 0.3% to near 100%. We found no significant correlation of glucose breath test results with either the number of bacterial colonies or with the DNA‐based bacterial cell counts. Instead, higher signals in the hydrogen‐methane breath test were significantly correlated with a lower viability of jejunal bacteria, at a P‐value of .014.
Conclusions & Inferences
The glucose‐based hydrogen and methane breath test is not sensitive to the overgrowth of jejunal bacteria. However, a positive breath test may indicate altered jejunal function and microbial dysbiosis.
Breath tests based on the production of hydrogen and methane from the metabolism of ingested glucose are often used to diagnose SIBO. We have found that in a group of patients under evaluation for SIBO, breath test results were not correlated with either PCR‐quantified bacterial DNA or live bacterial counts in jejunal aspirate samples collected during endoscopy. Although the glucose breath test does not appear useful for detecting SIBO, a positive breath test is correlated with low bacterial viability, which may indicate other types of jejunal and dysfunction.