Study of CNCM I-1518 in Healthy and Colonized Elderly Gut Microbiota.

Consumption of probiotic bacteria can result in a transient colonization of the human gut and thereby in potential interactions with the commensal microbiota. In this study, we used novel PolyFermS continuous fermentation models to investigate interactions of the candidate probiotic strain CNCM I-1518 () with colonic microbiota from healthy elderly subjects using 16S rRNA gene amplicon sequencing and metatranscriptomics, or with microbiota -colonized with ( NCTC 13307 and DSM 1296)-an enteropathogen prevalent in the elderly population. Small changes in microbiota composition were detected upon daily addition of , including increased abundances of closely related genera and , and of the butyrate producer . Microbiota gene expression was also modulated by with distinct response of the transcriptome and an increase in carbohydrate utilization. However, no inhibitory effect of was observed on colonization in the intestinal models under the tested conditions. Our data suggest that, in the experimental conditions tested and independent of the host, has modulatory effects on both the composition and function of elderly gut microbiota without affecting growth and toxin production.