A randomised controlled trial of a probiotic Lactobacillus strain in healthy adults: Assessment of its delivery, transit and influence on microbial flora and enteric immunity

In several intestinal disease states, altered microflora, impaired gut barrier and/or intestinal inflammation offer a rationale for the effective therapeutic use of probiotic microorganisms. However, for most candidate probiotic organisms there is a lack of evidence detailing their characterisation and effects on host flora and immunity. We have previously reported the isolation and characterisation, from surgically resected segments of the human gastrointestinal tract (GIT), of potential probiotic lactic acid bacteria (LAB). We have also described subsequent animal experiments that evaluated the establishment, persistence and localisation of specific probiotic Lactobacillus strains within the murine intestinal tract, in addition to their ability to influence the development of murine inflammatory disorders. In these studies, transit and survival of Lactobacillus salivarius UCC118 at the ileum was demonstrated using enteral tube sampling of six healthy volunteers following consumption of a single dose (150 ml) of fermented milk-borne probiotic (10⁸ colony forming units per ml (CFU/ml)). Subsequently, we performed a randomised controlled trial of 80 volunteers fed strain UCC118 (10⁸ CFU/day for 21 d), using two oral delivery vehicles (fresh milk, n = 20 vs. fermented milk, n = 20; controls, n = 20 for each). Throughout this feeding period, and for up to 100 days following cessation of feeding, the numbers of total culturable lactobacilli and of the administered Lactobacillus UCC118 present in faeces were monitored. Five subjects (5/40; fresh milk, four; fermented milk, one) were still excreting the probiotic lactobacilli 21 days post-cessation of feeding, while one subject (fermented milk) was still colonised up to 100 days after feeding. Consumption of fermented milk-borne UCC118 cells resulted in significantly increased levels of faecal-borne enterococci and lactobacilli. Numbers of bifidobacteria, coliforms and bacteroides were not significantly altered. In addition, changes in salivary IgA levels against UCC118 cells and increased granulocyte phagocytic activity were observed following consumption of the fermented milk-borne probiotic. In summary, Lactobacillus UCC118 was found to effectively transit (and persist within) the human intestinal tract, to modify the faecal flora and to engage the immune system.