Impact of Oral Administration of Lactobacillus reuteri LMG-P 27481 on Human Gut Microbiota Diversity and Function: A Pilot Study

<b>Background</b>: Many literature studies have reported the beneficial effects of probiotics on human health, but few articles have evaluated their "real effects" on the modulation of microbiota after their use. <i>Lactobacillus reuteri</i> (<i>L. reuteri</i>) is one of the most studied probiotics with the best effects on gut microbiota. <b>Aims</b>: The primary aim of our study was the evaluation of the intestinal colonization by <i>L. reuteri</i>-LMG P 27481 and its effects on the modification of the gut bacterial flora. The secondary aim was the evaluation of side effects through the validated Gastrointestinal Symptom Rating Scale (GSRS). <b>Patients and Methods</b>: This is an interventional, open-label study conducted on 20 healthy adults (10 men and 10 women M/F; mean age 34 ±15 years) who received a probiotic Reuterin^® LMG (<i>L. reuteri</i> LMG P 27481) for 28 consecutive days in drops at a concentration of 1 × 10⁹ (five drops per day). Microbiota analysis was performed at enrollment (T0), at the end of probiotic supplementation (T1) and after a 14-day follow-up period (T2). <b>Results</b>: In our study we observed interesting quantitative and functional variations as regards the Firmicutes/Bacterioidetes ratio, intestinal permeability, and the production of short-chain fatty acids (SCFA). This probiotic was safe and was able to improve patients' symptoms. <b>Conclusions</b>: The intake of <i>L. reuteri</i> LMG-P 27481 in healthy subjects showed transitory variations in some functional and metabolic gut functions, especially an improvement in the barrier effect and intestinal permeability, y and an increase in SCFA. Future studies should include target populations to have a greater range for modulation of the gut microbiota.