Potential fate of ingested Lactobacillus plantarum and its occurrence in human feces.

Lactobacillus plantarum has been used in human clinical trials to promote beneficial effects in the immune system, to alleviate intestinal disorders, and to reduce the risk of cardiovascular disease. It is also involved in many fermentation processes in the food industry. However, information on the fate of ingested L. plantarum is limited. In this study, 61 subjects received daily doses of fermented milk containing 2 × 10(11) cells of L. plantarum Lp115 for different periods of time. The target microorganism was monitored in the fecal microbiota via quantitative PCR (qPCR). L. plantarum was detected and quantified in all of the subjects during the ingestion periods. The differences between the L. plantarum levels at time zero and during all the different ingestion periods were statistically significant (P = 0.001). However, at 15 and 45 days after discontinuing supplementation, the number of lactobacilli was reduced to the baseline level (those at time zero). A longer period with L. plantarum in the diet did not result in increased levels of this bacterium in the stool, based on postconsumption evaluations (P = 0.001). The qPCR method was specific and sensitive for L. plantarum quantification in such a complex microbial environment as the gastrointestinal tract.