The fecal abundance of Collinsella aerofaciens and other potential pathobionts may predict the clinical efficacy of the probiotic Lacticaseibacillus paracasei DG in nonconstipated IBS patients

Background: Probiotics are exploited for adjuvant treatment in IBS but a reliable guidance for the selection of the appropriate probiotic to adopt for the different forms of IBS is lacking. Aim: To identify markers for the recognition of nonconstipated (NC) IBS patients that may have significant clinical improvements upon treatment with the probiotic strain Lacticaseibacillus paracasei DG (LDG). Methods: Post-hoc analysis of samples collected during a multi-centre, randomized, double-blind, parallel-group, placebo-controlled trial, in which NC-IBS patients were randomized to receive at least 24 billion CFU LDG or placebo capsules b.i.d. for 12 weeks. Primary clinical endpoint was the composite response based on improved abdominal pain and fecal type. Fecal microbiome and serum markers of intestinal, liver and kidney functionality were investigated. Results: Responders (R) in the probiotic arm (25%) differed from non-responders (NR) based on the abundance of 18 bacterial taxa including the family Coriobacteriaceae, Dorea spp., and Collinsella aerofaciens, which were overrepresented in R patients. These taxa also distinguished R (but not NR) from healthy controls. The probiotic intervention significantly reduced the abundance of these bacteria in R but not in NR. Analogous results emerged for C. aerofaciens from the analysis of data of a previous trial performed on IBS with the same probiotic. Finally, C. aerofaciens positively correlated with PV-1 and markers of liver functionality. Conclusions: LDG is effective on NC-IBS patients with a greater abundance of potential pathobionts. Among these, C. aerofaciens emerges as a potential predictor of the efficacy of the probiotic.