Selection and characterization of the probiotic potential of some lactic acid bacteria isolated from infant feces

Despite the important progress made in the field of probiotics. prediction of the precise mechanism of action is difficult, due, on one side to the complex interactions that can occur between food, microbes and host cells and on the other side, to the fact that the probiotic effect is strain dependent. Most of probiotic products are containing lactic acid bacteria (LAB). microorganisms considered as commensal and harmless for the host organisms. The purpose of the present work was to characterize the probiotic effects of three Lactococcus lactis strains isolated from breast fed Want feces (resistance to pH variation and taurocholic acid sodium salt concentrations, antimicrobial activity, ability to metabolize lactose and cholesterol, the ability to adhere to eukaryotic cells and competition with enteropathogenic Salmonella enteritidis, Shigella flexnerii and enteropathogenic Escherichia coli, immunomodulatory effect). The tested strains showed an increased resistance to a wide pH range of 3.0 to 8.0, as well as to thauroglicolate concentrations. from 0.5 to 3%, these features representing great advantages for the survival of these bacteria. once introduced in the gastrointestinal tract. Our strains reduced the serum cholesterol with an average of 45%. The three strains lacked mutual inhibition and high inhibitory activity of pathogenic or potentially pathogenic strains growth, demonstrating their potential use in the treatment of pediatric gastro-intestinal disorders, as an alternative or in association with antibiotics. The immunomodulatory studies demonstrated that the probiotic culture fractions are modulating the expression of the most important cytokines in the development of the anti-infectious immunity against enteric pathogens, expressed by the stimulation of TNF-alpha and INF-gamma pro-inflammatory cytokines and the inhibition of IL-6 and IL-8 cytokines, known to be implicated in the occurrence of lesional effects upon the infected host.