Baseline gut microbial profiles are associated with the efficacy of Bacillus subtilis and Enterococcus faecium in IBS-D

Abstract

Objective Little is known about association between the efficacy of probiotics and baseline gut microbiota in irritable bowel syndrome (IBS). We aimed to explore gut microbiota in diarrhea-predominant IBS (IBS-D) and whether baseline gut microbiota was related to the efficacy of Bacillus subtilis and Enterococcus faecium (BE). Methods This study recruited 19 healthy controls (HC) and 50 IBS-D patients, among whom 19 patients were administrated 500 mg BE orally three times daily for 2 weeks. Clinical data and fecal samples were collected from patients before and after treatment. 16S rRNA sequencing was performed to obtain fecal bacterial data. Results There was no significant difference of alpha diversity, beta diversity, profiles of microbial phyla and genera between HC and IBS. BE improved IBS-SSS (IBS severity scoring system) and stool consistency, and altered Enterococcus, Blautia, Lachnoclostridium and Fusobacterium without significant impact on microbial structure in IBS-D. Notably, baseline fecal bacterial composition differed between non-responders and responders to BE concerning abdominal pain and bloating, with Atopobium, Pyramidobacter, Ruminococcus gnavus and Peptostreptococcus enriched in responders in terms of abdominal pain. There was reduced abundance of Prevotella, Ruminococcaceae UCG, Eubacterium eligens, Faecalibacterium and Eubacterium coprostanoligenes in responders compared with non-responders. Furthermore, BE increased beneficial bacteria including Faecalibacterium, Blautia and Butyricicoccus, decreased Lachnoclostridium and Bilophila, and influenced some microbial metabolic pathways in responders, such as mineral absorption, metabolism of arachidonic acid, d-arginine, D-ornithine, phenylalanine and vitamin B6. Conclusion Baseline fecal microbiome is associated with the efficacy of BE in attenuating abdominal pain and bloating in IBS-D.