Quantitative evaluation of synbiotic strategies to improve persistence and metabolic activity of Lactobacillus reuteri DSM 17938 in the human gastrointestinal tract

The efficacy of three synbiotic approaches to improve persistence and metabolic activity of Lactobacillus reuteri DSM 17938 in the human gut was determined in a single-blind, randomized, crossover, placebo-controlled trial. Synbiotics consisting of 5 × 108 bacterial cells and 2 g of either GOS, rhamnose or the combination of both were given to 15 healthy adults for 7 days, followed by 10 days during which only the carbohydrates were administered. Faecal samples were collected and quantitative real-time PCR was used to determine cell numbers and rRNA copy number. Although L. reuteri DSM 17938 was detectable in faecal samples after consumption, the addition of GOS, rhamnose, and the mixture of the both did not increase faecal populations, nor was persistence enhanced after consumption of the probiotic had ended. However, based on rRNA per cell ratios, the combination of GOS and rhamnose significantly stimulated metabolic activity of the L. reuteri strain.