Introduction

Gut dysbiosis is implicated in various gastrointestinal and metabolic diseases. Probiotics is known to have favorable effects on gut microbiota and the production of essential short chain fatty acids (SCFA), albeit with inconsistent findings. The effects of bowel cleansing on the intestinal microbiota have been characterized, however the impact of administering probiotics following a colonic lavage on the intestinal microbiota has not been studied. Rifaximin has also been shown inconsistently in studies to affect the gut microbiome. In addition, treatment with probiotic for a duration of 4 weeks was demonstrated to modulate intestinal bacterial taxa in healthy adults. This pilot study examined the effects of a probiotic (vivomixx), with and without pre-treatment with colonic lavage or rifaximin, on the gut microbiome, SCFA and its recovery.

Aims & Methods

This is a single centre, exploratory randomized controlled study on healthy Asian adult volunteers. Participants were randomized equally to four study groups: (A) Colonic lavage using polyethylene glycol (PEG), followed by 4 weeks of vivomixx; (B) Colonic lavage, followed by 4 weeks of placebo; (C) 4 weeks of vivomixx; and (D) 2 weeks of rifaximin, followed by 4 weeks of vivomixx. Stool samples were collected at baseline, 4 weeks and 8 weeks after the administration of vivomixx or placebo. Additionally, Group A, B and D had stools collected before and after administration of PEG (Group A, B) or rifaximin (Group D). All stools were subjected to 16S rRNA sequencing for microbiome and SCFA analysis by gas chromatography mass spectrometry.

Results

A total of 32 participants were recruited, 1 in Group C dropped out after the first visit, leaving 31 in the final analysis. All three exposure elements – PEG, rifaximin and vivomixx resulted in large microbiome composition changes. Exposure of PEG also resulted in significant changes to SCFA concentrations. Pre-treatment with colonic lavage deterred engraftment as evidenced by the smaller increase in abundance of Bifidobacterium in Group A and B as compared to those without PEG (Group C). There was apparent selective engraftment of Lactobacillus after rifaximin treatment (Group D) and this was also shown in the SCFA analysis where the concentrations of Acetic, Butyric and Propionic acids, which are byproducts of Lactobacillus increased after Rifaximin treatment prior to vivomixx. This increase seems sustained at 8 weeks. There was also a trend of sustained vivomixx effects on gut microbiome at 4 weeks after stopping the probiotic.

Conclusion

Vivomixx demonstrated favorable impact on gut microbiome composition but its impact on SCFA in this study was minimal. Rifaximin however, has been shown to increase SCFA concentrations and this increase was sustained 8 weeks after probiotics was given. The data provide valuable insights for designing future trials. The modulation of gut microbiome and SCFA is a potential treatment target in diseases associated with gut dysbiosis.

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