In vitro selection of some lactic acid bacteria strains with probiotic potential

Develloping new stategies for the prevention and treatment of bacterial infections became a major international problem, the probiotic products based on lactic acid bacteria (LAB) strains representing an alternative. The aim of this study was to investigate the antimicrobial activity of LAB strains, the virulence factors, the ability to survive the simulated gastro-intestinal (GI) conditions and antibiotic susceptibility, in order to select effective and safe probiotic strains. A number of 170 LAB strains were subjected to screening tests regarding the safety assessment and probiotic properties. The probiotic potential was investigated by detection of bacteriocin production, antimicrobial and gastro-intestinal survival tests. The safety of probiotic LAB strains was evaluated by antibiotic susceptibility tests and screenin for soluble virulence factors. Over 75% of strains showed antimicrobial activity and were selected for future studies. About 40% of LAB presenting hemolitic activity were removed from the study. From the remaining strains, 44 (42.7%) showed high resistance to GI condition, and were selected for antibiotic susceptibility tests. To prevent the risk of horizontal genes transfer to the intestinal pathogens, 23 strains presenting acquired antibiotic resistance were removed from the study. Finally, we selected 21 safe probiotic LAB strains which can be used in probiotic products.