In Vitro Study Of Lactobacillus LB-19 An-tibacterial Entero-pathogen Bacterial And Inhibition Them Adhesion On Caco-2 Cells

This study has determined the taxonomy position of Lactobacillus LB-19 (LB-19) by conventional bacteriological identification and 16SrDNA sequence analysis. And the anti-bacteria of LB-19 and its spent culture supernatant (SCS) to Enterotoxin-genic E.coli (ETEC) and Salmonella Choleraesuis, (S.Choleraesuis) was conducted in vitro. Simutanuesly, Human Enterocyte-Like Caco-2 cell as the experimental model to investigate the adhesion properties of LB-19, and the exclusion, competitive and displacement effect to ETEC and S. Choleraesuis was conducted too.The identification of LB-19 shows that the morphological characteristics, physiological and biochemical reaction results were much similar to Lactobacillus Johnsonii, and the homology of 16SrDNA gene sequence was reached 99%. Therefore, LB-19 was determined and named ultimately as Lactobacillus Johnsonii LB-19.In vitro anti-bacterial test shows that while LB-19 co-incubation with ETEC and S. Choleraesuis in different proportions for 16h, the inhibition proportion was reach 99.32% and 96.95% while in 1:1 mixed cultured, and this inhibition proportion get stronger as the concentration of LB-19 increased. After 24h co-incubation, all proportion of inhibition ratio was 100.00%. SCS antibacterial trail showed that only pH<4.0 SCS could produce significant inhibition on ETEC and S. Choleraesuis, and the lower pH, the better antibacterial; However , the inhibition effect of pH2.0 SCS(18.6±0.15mm and 20.5±0.28mm) was 2.5 times to pH2.0 of pure HC1 solution (7.83±1.10mm and 8.00±1.23mm).Adhesion results showed that the adhesion number of LB-19 with SCS suspended (25.05±3.92 bacteria/cell) was approximately 2 times compared with the same conditions use DMEM liquid suspensions(11.51±3.20bacteria/cell); between 1.Ox10CFU/mL to 1.0x109CFU/mL and 0.5-6h incubation times, the adhesion number of LB-19 was significantly increased as growth of the concentration and the times extension, after 1.0x109CFU/mL 6h adhesion, the growth trend has slowed down significantly.The adhesion inhibition result confirmed that 1.0x109CFU/mL LB-19 has a strong exclusive, competitive and displacement effect against ETEC and S. Choleraesuis adherence to Caco-2 cells, and the inhibition rate was reach 99.96%,99.97%,99.88%和95.00%,100.00%,99.83%.