Lavryk G. Characteristics of biological properties of lactobacilli based on in vivo and in vitro interaction with autochthonous and pathogenic microbiota

The dissertation is devoted to the results of a comparative study of the biological properties of indigenous lactobacilli and the assessment of the nature of their interaction with probiotic strains and other microorganisms. Dominance in all ecological niches of L. acidophilus species was established (30.3%). Heteroenzymatic lactobacilli predominated in all ecosystems. The probiotic strain L. plantarum 8R-A3 showed the highest antagonistic activity against gram-negative bacteria, and L. plantarum P17630 - against fungi of the genus Candida. The correlation between antimicrobial susceptibility of lactobacilli isolates and the microbiota according to the niches they inhabit has been established. Oropharyngeal isolates of lactobacilli are characterized by sensitivity to antimicrobial drugs, which is typical for the gram-positive microflora inhabiting the pharynx, and some intestinal isolates are characterized by sensitivity similar to that of enterobacteria. Irreversible ultrastructural changes in biofilm-forming staphylococci under the influence of probiotic strains of lactobacilli were proven, while in mixed cultures with indigenous isolates of lactobacilli, staphylococci acquired the ability to transfer into an inactive state. It has been proven for the first time that in a mixed culture, lactic acid bacteria are able to induce the death of staphylococci in biofilm form without converting it to planktonic, and also it was observed growth of lactobacilli (probiotic and indigenous isolates) on glucose agar (1%) under aerobic conditions after their isolation from mixed cultures with biofilm-forming staphylococci.