Preliminary screening of lactic acid bacteria against Escherichia coli and the research of probiotic potential for the screening bacteria

In order to select lactic acid bacteria which have the ability to inhibit the growth of Escherichia coli,ATCC25922 was used as the indicator bacterium,the culture supernatant from lactic acid bacteria were used to determine if there were antimicrobial activities to the pathogenic Escherichia coli,using Oxford- cup tests. Three lactic acid bacteria were screened and all of these were determined as Lactobacillus acidophilus by phylogenetic analyses of 16 S rRNA gene.Subsequently,the tolerance to gastric acidity and bile salts and antibiotic sensitivity of the Lactobacillus acidophilus were further evaluated.The results showed that KLDS1.0901 had the best tolerance to gastric acidity,KLDS1.0902 and KLDS1.1003 had the closer tolerance ability to gastric acidity,compared Lactobacillus acidophilus NCFM.For the tolerance to bile salts,Lactobacillus acidophilus NCFM had the best bile tolerance ability and KLDS1.0902 had the weakest ability,there were no considerable differences among KLDS1.0901,KLDS1.1003 and Lactobacillus acidophilus NCFM for bile tolerance ability.All of strains showed similar results in the sensitivity to antibiotics,showing tolerance to aminoglycoside antibiotics. Therefore KLDS1.0901 and KLDS1.1003 had the better probiotic potential,compared KLDS1.0902.The antimicrobial effects of KLDS1.0901 and KLDS1.1003 against the pathogenic Escherichia Coli should be further studied in cellular and animal models.