In-Vitro Growth Inhibition of Bacterial Pathogens by Probiotics and a Synbiotic: Product Composition Matters

A variety of activities potentially contribute to the beneficial effects of probiotic bacteria observed in humans. Among these is a direct inhibition of the growth of pathogenic bacteria in the gut. The present study characterizes head-to-head the in-vitro pathogen growth inhibition of clinically relevant infectious bacterial strains by different types of probiotics and a synbiotic. In-vitro growth inhibition of Escherichia (E.) coli EPEC, Shigella (Sh.) sonnei, Salmonella (S.) typhimurium, Klebsiella (K.) pneumoniae and Clostridioides (C.) difficile were determined. Investigated products were a yeast mono strain probiotic containing Saccharomyces (Sac.) boulardii, bacterial mono strain probiotics containing either Lactobacillus (L.) rhamnosus GG or L. reuteri DSM 17938, a multi strain probiotic containing three L. rhamnosus strains (E/N, Oxy, Pen), and a multi strain synbiotic containing nine different probiotic bacterial strains and the prebiotic fructooligosaccharides (FOS). Inhibition of pathogens was moderate by Sac. boulardii and L. rhamnosus GG, medium by L. reuteri DSM 17938 and the L. rhamnosus E/N, Oxy, Pen mixture and strong by the multi strain synbiotic. Head-to-head in-vitro pathogen growth inhibition experiments can be used to differentiate products from different categories containing probiotic microorganisms and can support the selection process of products for further clinical evaluation.