Probiotics have great value for restoration of balance of intestines. But the optimal use of probiotics demands the detailed description of bacterial strains. It has been shown the antagonistic potential of E.coli G35 N59 and 61 strains (which are symbiotic components of "Okarin") concerning pathogens in experiences in vitro and in vivo (Enterobacter, Klebsiella, Proteus, Citrobacter), and also their influence on quantitative structure of antibiotic resistance intestinal commensal E. coli.