RESUMO
INTRODUCTION: The therapeutic effect of probiotics for irritable bowel syndrome (IBS) was controversial. This study aims to evaluate the short-term efficacy of Bifidobacterium quadruple viable tablet in patients with diarrhea-predominant IBS and explore factors associated with response to probiotics. METHODS: A randomized, double-blind, placebo-controlled, multicenter trial was performed in 15 hospitals. A total of 290 patients who fulfilled the eligibility criteria were assigned to the probiotics or placebo group randomly with a ratio of 1:1 for a 4-week treatment and a 2-week follow-up. The primary outcome was the response rate. It was regarded as the proportion of patients with composite responses of improvement in both abdominal pain and diarrhea simultaneously. RESULTS: After 4-week continuous administration, the response rates of the probiotics and the placebo were 67.59% and 36.55%, respectively ( P < 0.001). In the probiotics, those with higher abdominal pain scores (2.674 [1.139-6.279]) were more likely to respond, but responders in placebo had lower Hamilton Depression Scale score (0.162 [0.060-0.439]), lower Hamilton Anxiety Scale score (0.335 [0.148-0.755]), and higher degree of bloating (2.718 [1.217-6.074]). Although the diversity of the microbiota was not significantly changed by probiotics, the abundance of bacteria producing short-chain fatty acids (SCFAs), including Butyricimonas ( P = 0.048), Pseudobutyrivibrio ( P = 0.005), Barnesiella ( P = 0.020), and Sutterella ( P = 0.020), and the concentration of SCFAs including butyric acid ( P = 0.010), valeric acid ( P = 0.019), and caproic acid ( P = 0.046) in feces increased. DISCUSSION: A Bifidobacterium quadruple viable tablet had a significant short-term efficacy for the treatment of diarrhea-predominant IBS and was more effective in patients with higher abdominal pain scores. This kind of probiotics could improve the abundance of several bacteria producing SCFAs and the concentration of fecal SCFAs compared with placebos.