LAUSR

Backgrounds Recent studies suggest that diarrhea-predominant irritable bowel syndrome (IBS) is associated with intestinal bacterial microflora, colonic inflammation, and small intestinal bacterial overgrowth (SIBO). The purpose of this study was to evaluate the effect of a multistrain probiotic intake on these associated factors in patients with diarrhea-predominant IBS. Methods The recruited volunteers were adults who were diagnosed with diarrhea-predominant IBS according to the Rome III criteria. After 8 weeks of probiotic ingestion, changes in gastrointestinal symptoms, fecal microbiome, SIBO, and fecal calprotectin were determined. Results There was an increase in beneficial bacteria (41.2 ± 16.8% vs. 53.7 ± 15.3%, P = 0.018) and a decrease in harmful bacteria (13.0 ± 13.9% vs. 4.7 ± 4.0%, P = 0.010) in the microbial stool analysis. The SIBO prevalence also decreased at the end of treatment. However, the average levels of fecal calprotectin showed a decreasing tendency, without reaching statistical significance (364.4 ± 729.1 mg/kg vs. 200.9 ± 347.6 mg/kg, P = 0.375). Conclusion Treatment with a multistrain probiotic for 8 weeks led to significant increases in beneficial bacteria in the gut as well as the improvement of gastrointestinal symptoms. This study is registered at the Clinical Research Information Service (KCT0002906).