Lactic acid bacteria termed probiotics have preventive as well as curative effects on several types of diarrhoea of different aetiologies. The main objective of this study was to screen lactobacilli strains having probiotic traits, isolated from Algerian healthy children faeces on the purpose of using them further in children diarrheal illnesses. One hundred and twenty (120) lactic acid bacteria isolates were selected from faecal samples of healthy Algerian children aged between five and ten years. Gram positive rods and catalase negative bacteria (52 isolates) were screened, in vitro, for their probiotic potential properties including ability to survive in simulated gastro-intestinal conditions, adherence to Caco-2 cells and their antimicrobial activity. The results show that only five strains resisted in simulated gastric juice at pH 1.5 and pepsin. Four of them were resistant to simulated intestinal conditions at pH 8 and pancreatin and have a good adherence. In the end, three of them were retained as they display interesting probiotic profiles characterized by a strong antimicrobial effect against some intestinal pathogenic bacteria. They were identified by 16S rDNA sequencing as Lactobacillus plantarum F12, Lactobacillus brevis G6 and Lactobacillus paracasei B13.
The strain, Lactobacillus plantarum F12 with probiotic traits was isolated from Algerian healthy children faeces and identified by 16S rDNA sequencing. In this study, the antimicrobial activity and physicochemical properties of bacteriocin-like substance (BLS) produced by this strain were determined. Also, the bacteriocinogenic genes of plantaricin A, plantaricin J and plantaricin K were screened in this strain. The BLS inhibited a range of pathogenic and spoilage bacteria including Escherichia coli, Salmonella infantis, Salmonella typhimurium, Shigella sonnei, Staphylococcus aureus, Listeria monocytogenes, Listeria innocua, Bacillus subtilis and some lactobacilli sp. The BLS was proteinaceous since it was inactivated by the proteolytic enzymes (trypsin, proteinase K and pronase) but not by α-amylase and lipase. It was heat stable at different temperatures (40 -121°C) for 30 min and retained its activity at a wide range of pH values (2 to 10). Its activity was totally preserved at -80°C for 120 days and at -20°C for 60 days. The amplification of genetic determinants of plnA, plnJ and plnK has shown the presence of these genes in L. plantarum F12. The ability of the BLS from L. plantarum F12 to inhibit several pathogenic/spoilage bacteria and its characterization demonstrated its interest as a natural food preservative, in addition to its probiotic potential in prevention and treatment of infectious diseases.
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