A probiotic formulation of Enterococcus faecium R0026 and Bacillus subtilis R0179 has been evaluated in previous clinical trials. However, B. subtilis R0179 has not been evaluated as a single probiotic strain or in combination with other strains at doses higher than 0.1×109 cfu. To establish oral dose-response tolerance and gastrointestinal (GI) viability of B. subtilis R0179, a randomised, double-blind, placebo-controlled trial in healthy adults (n=81; 18-50 years old) was conducted. Participants received B. subtilis R0179 at 0.1, 1.0 or 10×109 cfu/capsule/day or placebo for four weeks. General wellness was assessed using a daily questionnaire evaluating GI, cephalic, ear-nose-throat, behavioural, emetic, and epidermal symptoms. GI symptoms were further evaluated using a weekly gastrointestinal symptom rating scale (GSRS). GI transit viability of B. subtilis R0179 was assessed by plating and microbiota analysis by 16S rRNA at baseline, week 4 of the intervention and washout. General wellness and GI function were not affected by oral consumption of B. subtilis R0179 at any dose. Daily questionnaire syndrome scores were not different from baseline and did not exceed a clinically significant score of 1. GSRS syndrome scores were not different from baseline and ranged from 1.1±0.1 to 1.9±0.2. Faecal viable counts of B. subtilis R0179 demonstrated a dose response: the placebo group (1.1±0.1 log10 cfu/g) differed from 0.1×109 (4.6±0.1 log10 cfu/g), 1×109 (5.6±0.1 log10 cfu/g) and 10×109 (6.4±0.1 log10 cfu/g) (P<0.0001). No significant changes in phyla were observed, but sequence reads binned to multiple operational taxonomic units matching closest to Ruminococci increased during probiotic supplementation. B. subtilis R0179 survives passage through the human GI tract and is well tolerated by healthy adults at intakes from 0.1 to 10×109 cfu/day. The trial has been registered at www.clinicaltrials.gov under NCT01802151.
Keywords: GSRS; gastrointestinal symptoms; microbiota; probiotic; viability.