Impact of Saccharomyces boulardii CNCM I-745 on bacterial overgrowth and composition of intestinal microbiota in IBS-D patients: results of a randomized pilot study

BackgroundSmall intestinal bacterial overgrowth (SIBO) is associated with diarrhea-predominant irritable bowel syndrome (IBS-D). Probiotics like S. boulardii CNCM I-745 (Sb) may be efficacious in balancing the microbiota.This randomized open label study assessed the effect of Sb in patients with bacterial overgrowth associated with IBS-D and its impact on the intestinal microbiota.MethodsPatients were randomized to receive for 15 days; S. boulardii + dietary advice (Sb+DA) or dietary advice (DA) only. SIBO was assessed by the lactulose hydrogen breath test (LHBT). Symptoms were assessed with the IBS Symptom Severity Scale (IBS-SSS) and stool consistency with the Bristol Stool Form Scale. Microbiota and mycobiota were analyzed by 16S rDNA and ITS2.Results 54 patients were included, among them 48 (27 Sb+DA, 21 DA) were evaluated. Decrease of hydrogen excretion was slightly higher in Sb+DA group, 41% vs 29% in DA group, and IBS-SSS total score were reduced by -134 and -93, respectively The proportion of patients with diarrhea was lower in the Sb+DA group than in the DA group (25.9% compared to 47.6%)Bacterial and fungal microbiota showed that S. boulardii CNCM I-745 treatment was associated with several modifications. Interestingly, F. prausnitzii was more abundant in Sb-treated patients with marked clinical improvement. The safety of Sb was excellent.ConclusionsIn patients with SIBO, S. boulardii CNCM I-745 associated with dietary advice reduced bacterial overgrowth and improved digestive symptoms while restoring the intestinal microbiota. The increased abundance of F. prausnitzii coupled with symptom improvement merits further research.