Knowledge of the intra-individual spatial and regional distribution of intestinal microbial populations is essential to understand gut host–microbial interactions. In this study, we performed a compositional analysis of luminal and mucosal samples from the small and large intestine of four organ donors by 16S rRNA amplicon sequencing and high-throughput quantitative polymerase chain reaction. Since the human microbiota is subject to selection pressure at lower taxonomic levels, we isolated over 400 bacterial strains and investigated strain-level variation of 11 Lactobacillus rhamnosus from different intestinal regions. Results substantiate reported inter-individual variability as well as intra-individual differences along the gastrointestinal tract. Although the luminal and mucosal-associated communities were similar within individuals, relative abundance reflected the donors’ demographic and potential pathologies. The total bacterial load of all donors increased from small intestine to colon, while Bifidobacterium was in greater abundance in the small intestine. Comparative genomic analysis of L. rhamnosus showed the strains segregated into two distinct clusters and identified no features specific to location. Analysis revealed genetic differences for exopolysaccharide production, carbohydrate utilization, pilus formation and vitamin K biosynthesis between clusters. This study contributes to the understanding of niche-specific microbial communities, encouraging subsequent studies to better understand microbial signatures at lower taxonomic levels.

Broad-spectrum antibiotic use can disrupt the gastrointestinal microbiota resulting in diarrhoea. Probiotics may be beneficial in managing this type of diarrhoea. The aim of this 10-week randomised, double-blind, placebo-controlled, parallel study was to investigate the effect of Lactobacillus helveticus R0052 and Lactobacillus rhamnosus R0011 supplementation on antibiotic-associated diarrhoea in healthy adults. Subjects were randomised to receive 1 week of amoxicillin–clavulanic acid (875 mg/125 mg) once per day, plus a daily dose of 8×109 colony-forming units of a multi-strain probiotic (n 80) or placebo (n 80). The probiotic or placebo intervention was maintained for 1 week after completion of the antibiotic. Primary study outcomes of consistency and frequency of bowel movements were not significantly different between the probiotic and placebo groups. The secondary outcomes of diarrhoea-like defecations, Gastrointestinal Symptoms Rating Scale scores, safety parameters and adverse events were not significantly different between the probiotic intervention and the placebo. A post hoc analysis on the duration of diarrhoea-like defecations showed that probiotic intervention reduced the length of these events by 1 full day (probiotic, 2·70 (sem 0·36) d; placebo, 3·71 (sem 0·36) d; P=0·037; effect size=0·52). In conclusion, this study provides novel evidence that L. helveticus R0052 and L. rhamnosus R0011 supplementation significantly reduced the duration of diarrhoea-like defecations in healthy adults receiving antibiotics.

In Europe, the species Lactobacillus rhamnosus is currently on the Qualified Presumption of Safety list used by the European Food Safety Authority (EFSA) for internal safety assessment, but according to the EFSA the species should remain a topic of surveillance. In the present study, the safety and tolerance of the potentially probiotic strain L. rhamnosus PRSF-L477 was investigated in a placebo-controlled double-blind volunteer trial following FAO/WHO guidelines. A total of thirty-four subjects received daily doses of 1 × 1011 colony-forming units (cfu) of L. rhamnosus PRSF-L477 (n 17) or placebo (n 17) for a period of 3 weeks, followed by a wash-out period of another 3 weeks. A questionnaire on gastrointestinal tolerance and a diary was kept daily to record compliance throughout these 6 weeks. Faecal and blood samples were collected for microbiological and haematological analysis. The recorded gastrointestinal symptoms, defecation frequency and stool consistency were not influenced indicating that L. rhamnosus PRSF-L477 was well tolerated. The species L. rhamnosus was detected in the faeces of sixteen out of seventeen subjects of the probiotic group during the intervention period. Using pulsed-field gel electrophoresis, re-isolates of L. rhamnosus PRSF-L477 were confirmed in nine of these subjects. Antibiotic susceptibility profiles of these re-isolates were unchanged compared with PRSF-L477. No clinically relevant changes in blood parameters such as liver and kidney function and no serious adverse events appeared during and after administration. Therefore, we conclude that L. rhamnosus PRSF-L477 can safely be administrated to healthy subjects at a daily dose of 1 × 1011 cfu.

Unsupplemented acid goat whey containing 0·96% protein and 2·76% lactose was fermented aerobically with 32 microflora extracted from various raw milk cheeses and dairy products. These microflora were screened for their ability to hydrolyse whey proteins (α-lactalbumin and/or β-lactoglobulin) and to generate peptides inhibitors of Angiotensin I Converting Enzyme. Five microflora were able to degrade whey protein. The most efficient microflora was able to fully hydrolyse α-lactalbumin and to a lesser extend β-lactoglobulin. It was extracted from Bamalou des Pyrenées cheese. Micro-organisms involved consisted of yeast Kluyveromyces marxianus and lactobacillus Lactobacillus rhamnosus. Both were able to produce ACE inhibitory peptides after whey fermentation.