Methanogen Abundance Thresholds Capable of Differentiating In Vitro Methane Production in Human Stool Samples.

BACKGROUND

Intestinal methane (CH) gas production has been associated with a number of clinical conditions and may have important metabolic and physiological effects.

AIMS

In this study, taxonomic and functional gene analyses and in vitro CH gas measurements were used to determine if molecular markers can potentially serve as clinical tests for colonic CH production.

METHODS

We performed a cross-sectional study involving full stool samples collected from 33 healthy individuals. In vitro CH gas measurements were obtained after 2-h incubation of stool samples and used to characterize samples as CH positive (CH+) and CH negative (CH-; n = 10 and 23, respectively). Next, we characterized the fecal microbiota through high-throughput DNA sequencing with a particular emphasis on archaeal phylum Euryarchaeota. Finally, qPCR analyses, targeting the mcrA gene, were done to determine the ability to differentiate CH+ versus CH- samples and to delineate major methanogen species associated with CH production.

RESULTS

Methanobrevibacter was found to be the most abundant methane producer and its relative abundance provides a clear distinction between CH+ versus CH- samples. Its sequencing-based relative abundance detection threshold for CH production was calculated to be 0.097%. The qPCR-based detection threshold separating CH+ versus CH- samples, based on mcrA gene copies, was 5.2 × 10 copies/g.

CONCLUSION

Given the decreased time-burden placed on patients, a qPCR-based test on a fecal sample can become a valuable tool in clinical assessment of CH producing status.