The study of the antagonistic activity of the Lactococcus lactis subsp. lactis strain against pathogenic and opportunistic microbiota is a necessary condition for selecting cultures for bacterial preparations used in the production of fermented products. It was found that the Lactococcus lactis subsp. lactis strain did not affect the growth of Pseudomonas aeruginosa, Enterobacter aerogenes, and Proteus vulgaris. The most sensitive strain was Escherichia coli 055.