Influence of monostrain and multistrain probiotics on immunity, intestinal ultrastructure and microbiota in experimental dysbiosis

Abstract

The biological effects of three probiotic strains <i>Lactobacillus rhamnosus</i> K32, <i>Bifidobacterium longum</i> GT15, <i>Enterococcus faecium</i> L3 and their mixture were studied using a model of dysbiosis induced in rats by antibiotics. It was found that after taking different probiotics intestinal microbiota changed in a strain-specific manner. The maximal activity against pathogens was revealed after the administration of a mixture of bacterial strains under study or a single strain of enterococci. The strain <i>E. faecium</i> L3 showed the most activity against both <i>Klebsiella</i> spp. and <i>Bacteroides fragilis.</i> It helped to restore the original content of <i>Faecalibacterium prausnitzii</i>. The number of <i>Klebsiella</i> spp. was the same in the group receiving <i>L. rhamnosus</i> K32 and the group of animals, which was not consuming probiotics. Different probiotic strains included in the composition had various immunological effects. Probiotic bifidobacteria, enterococci and the mixture of three probiotics stimulated of mRNA expression of interleukin (IL)-10 in mesenteric lymph nodes. The changes in microbiota after consuming an enterococcal probiotic correlated with an increase in transforming growth factor (TGF)-β and IL-10 content in blood serum and an increase of the intestinal mucus layer. Consumption of <i>L. rhamnosus</i> K32 led to the stimulation of IL-8 expression in mesenteric lymph nodes. Control group not receiving probiotics was characterised by expression of pro-inflammatory cytokines, damage of epithelial cells and the destruction of their tight junctions. The damage to the ultrastructure of the mucosa was prevented in all the groups taking probiotics.