Identification of a species-specific bacterial signature in Parkinson’s and modification with a probiotic intervention

Abstract The gut-brain axis is a bi-directional signalling system that includes the enteric system, the gut microbiome (GM) and its metabolites. An unhealthy (dysbiotic) gut is associated with deleterious perturbation to the GM resulting in systemic inflammation thought to contribute to a range of conditions including Parkinson’s. Most studies investigating the human gut GM do not focus on species-level analyses needed to establish prevalence and abundance of commensal and pathobiont bacteria, and whether therapeutic interventions alter the GM composition. In this study we conducted an RCT where one group of people with Parkinson’s (PwP) was assigned to a probiotic arm and the other to placebo arm. Stool samples were collected sequenced and analysed at week 0 and week 12. Conventional bioinformatic analyses suggested changes to the GM of the placebo group at week 12 compared to placebo but lacked specificity and were uninformative. Through careful analyses of species-level data we established a species-specific-signature for PwP in our study and a positive effect of the probiotic (Symprove™) on the GM in those assigned to the probiotic arm. To conclude – bioinformatic analyses lack specificity when used with small samples, we detected a species-specific signature in our group of PwP by analysing species prevalence across individuals, and the therapeutic use of a 12-week probiotic improved the overall composition of the GM in probiotic compared to placebo group.