The purpose of this study was to investigate by in vitro studies the antimicrobial activity of eight lactic acid bacterial (LAB) strains belonging to Lactobacillus paracasei spp. paracasei, L. plantarum and L. rhamnosus species against Salmonella enteritidis, Shigella flexneri and EPEC pathogenic strains isolated from pediatric diarrhoea cases, simultaneously with the assessment of the cytotoxicity and immunomodulatory potential of the respective strains. The study of the adherence capacity to the cellular substrate represented by HeLa cells was performed by Cravioto’s adapted method. The cytotoxicity was determined on HeLa cells and the level of soluble pro- and anti-inflammatory cytokines was assessed by ELISA. Our in vitro studies are demonstrating that the selected probiotic strains are inhibiting the adherence and colonization of HeLa cells by the enteropathogenic strains isolated from pediatric diarrhoea mainly by direct competition for adherence sites, demonstrating their potential use in the treatment of pediatric gastro-intestinal disorders, as an alternative to/in association with antibiotics. A great advantage of the selected probiotic strains is their low cytotoxicity and ability to trigger a beneficial cytokine response in the epithelial cells, which potentiates their antimicrobial activity by stimulating the occurrence of a rapid immune response following the intestinal injury.
Key words: Antimicrobial activity, immunomodulatory, cytokines, invasive bacteria, Lactobacillus, enteropathogenic bacteria, antimicrobial effect, cytotoxicity, probiotics.
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