Oral administration of live exopolysaccharide-producing Pediococcus parvulus, but not purified exopolysaccharide, suppressed Enterobacteriaceae without affecting bacterial diversity in ceca of mice.

Growing evidence indicates that the gut microbiota could have an important role in the development of diet- and lifestyle-induced diseases. It has been shown that modulation of the gut microbiota by means of probiotics and prebiotics could improve host health. An oat-based product fermented by the exopolysaccharide (EPS)-producing organism Pediococcus parvulus 2.6 has been reported to have a bifidogenic effect. To find out whether the effect could be attributed to the EPS or the bacterium, mice were fed a diet supplemented with 2% purified EPS or 10(8) CFU/g of live P. parvulus 2.6 for 6 weeks. Both supplementations altered the gut microbiota composition but in different directions. Purified EPS not only significantly lowered the microbial diversity (P < 0.001) but decreased the bifidobacterial population (P = 0.01). In contrast, the live EPS-producing bacterium P. parvulus 2.6 antagonized Enterobacteriaceae without disturbing the homeostasis of the cecal microbiota.