The resistance/multidrug resistance of bacterial strains to antibiotics is a major public health problem both in Romania and worldwide. In Romania there is an increasing trend in the incidence of infections with bacterial strains that are highly resistant to antibiotics, a trend that is also accentuated by the production of bacterial biofilms in tissues or materials used in medicine. In our country the problem of developing alternative strategies for the prevention and treatment of infections with multi-drug resistant or biofilm-forming bacteria is less studied, despite the high potential for application in biomedicine and the usefulness of these strategies in restoring normal microbiota after the negative impact of antibiotics. One of the alternatives to conventional treatments is the use of probiotic products, which when administered in adequate quantities confer beneficial effects on human health. Optimal use of probiotic microorganisms requires an understanding of the mechanisms by which they act. The selection of a strain for inclusion in a probiotic preparation should be made on the basis of its ability to induce an improvement in the host's response without altering intestinal homeostasis. The main objective of this project involves complex studies on bacterial strains with probiotic potential (newly isolated lactic acid bacteria) and bacterial consortia in order to improve experimental protocols for the optimal selection of probiotics for human use based on their anti-infective and immunomodulatory activity.