Survival of Lactobacillus helveticus strain CP53 in the human gastrointestinal tract

A critical evaluation of the factors affecting the survival and persistence of beneficial bacteria in healthy adults

The efficacy of a probiotic depends on its ability to survive and persist in the digestive tract. Regulatory agencies around the world recommend minimum dosages in order for a product to be termed a probiotic. However, the effect of dosage on the survival of the bacteria in the gut - the primary objective of probiotic administration - has not been critically evaluated. We performed a systematic literature review to assess the available data on the survival rate, during gastrointestinal transit, of probiotic bacteria that were orally administered to healthy adults. We also evaluated the persistence of the administered strain(s) after discontinuation of treatment and the potential role played by the food matrix in which probiotics have been administered. From a regulatory perspective, the profile of the target population is key to establishing the efficacy of probiotics. Therefore, we focussed on subjects without disease conditions. We evaluated 17 studies of single strains and 13 studies of multi-strain products, which reported survival and persistence outcomes. Persistence in the gut and recovery from stool were strain dependent. When the administered dose was higher than 10¹⁰ cfu/day, the probiotic could be recovered from stool regardless of the strain used. Treatment duration did not affect faecal recovery. Thus, dosage recommendations for probiotics by regulatory agencies are lower than that required for a strain to survive, persist and be efficacious in the gut.

Genomic Comparison of Lactobacillus helveticus Strains Highlights Probiotic Potential

Lactobacillus helveticus belongs to the large group of lactic acid bacteria (LAB), which are the major players in the fermentation of a wide range of foods. LAB are also present in the human gut, which has often been exploited as a reservoir of potential novel probiotic strains, but several parameters need to be assessed before establishing their safety and potential use for human consumption. In the present study, six L. helveticus strains isolated from natural whey cultures were analyzed for their phenotype and genotype in exopolysaccharide (EPS) production, low pH and bile salt tolerance, bile salt hydrolase (BSH) activity, and antibiotic resistance profile. In addition, a comparative genomic investigation was performed between the six newly sequenced strains and the 51 publicly available genomes of L. helveticus to define the pangenome structure. The results indicate that the newly sequenced strain UC1267 and the deposited strain DSM 20075 can be considered good candidates for gut-adapted strains due to their ability to survive in the presence of 0.2% glycocholic acid (GCA) and 1% taurocholic and taurodeoxycholic acid (TDCA). Moreover, these strains had the highest bile salt deconjugation activity among the tested L. helveticus strains. Considering the safety profile, none of these strains presented antibiotic resistance phenotypically and/or at the genome level. The pangenome analysis revealed genes specific to the new isolates, such as enzymes related to folate biosynthesis in strains UC1266 and UC1267 and an integrated phage in strain UC1035. Finally, the presence of maltose-degrading enzymes and multiple copies of 6-phospho-β-glucosidase genes in our strains indicates the capability to metabolize sugars other than lactose, which is related solely to dairy niches.

Lactobacillus strain ecology and persistence within broiler chickens fed different diets: identification of persistent strains

Lactobacilli are autochthonous residents in the chicken gastrointestinal tract, where they may potentially be used as probiotics, competitive exclusion agents, or delivery vehicles. The aim of this study was to use an in vivo model to investigate the effect of diet and competing lactic acid bacteria on the colonization of inoculated Lactobacillus strains, with the goal of identifying strains which can consistently colonize or persist for an extended period of several weeks. Chicken-derived Lactobacillus strains were genetically marked with rifampin resistance and administered on day 0 to chickens fed either a normal commercial diet or a specially formulated high-protein diet. Chickens fed the high-protein diet were also coinoculated with two different mixes of additional lactic acid bacteria. Enterobacterial repetitive intergenic consensus sequence-based PCR (ERIC-PCR) was used to identify rifampin-resistant isolates recovered from chickens. Three strains, belonging to the species Lactobacillus agilis, Lactobacillus crispatus, and Lactobacillus vaginalis, were commonly reisolated from the chickens on both diets at days 21 and 42. The ability of these strains to persist was confirmed in a second chicken trial. All three strains persisted throughout the production period in the chickens fed a commercial diet, while only the L. agilis and L. vaginalis strains persisted in the chickens fed the high-protein diet. In both in vivo trials, competing lactic acid bacteria modified representation of the strains recovered, with all three stains capable of competing in the presence of one or both mixes of coinoculated strains. The in vivo model successfully identified three persistent strains that will be characterized further.

Monitoring the cell number and viability of Lactobacillus helveticus GCL1001 in human feces by PCR methods

Real-time polymerase chain reaction (PCR) and nested reverse transcription (RT) PCR were applied to demonstrate the viability of lactobacilli in the feces of volunteers fed fermented milk containing lactobacilli. Two sets of specific primers and a TaqMan probe for real-time PCR were constructed using the S-layer gene as a target. After fermented milk ingestion, Lactobacillus helveticus GCL1001 was detected in the feces of 12 volunteers over a few days, with the maximum number being between 10(4.5) and 10(7.8) cells g(-1) of feces. Moreover, mRNA from this strain was detected in the feces of all volunteers by nested RT-PCR. The results show that these methods are applicable to the demonstration of bacterial viability in feces, and that ingested L. helveticus GCL1001 can survive through the gastrointestinal tract.