The Screeing And Research Of Lactic Acid Bacteria And The Study For Antagonism Of Salmonella Infection

Lactic acid bacteria have attracted increasing much attention because of their potential application to probiotics. In this study, the lactic acid bacteria were isolated from the silage and yogurt. The isolated strains were identified according to the morphological characteristics, Gram stain, catalase tests, physiological and biochemical characteristics,16S rDNA sequence analysis and carbohydrate test. And the potential probiotic strains were screened through tolerated artificial gastric juice, toleranced bile salt, adhesion to the cells and stimulating cytokines secretion of BMDC. Screened 5 lactic acid bacteria that have the potential to induce Th1/Th2 type immune respons were administered orally for 6 weeks and challenged with salmonella typhimurium at the last. After challenge, the death rate and the body weight of different groups were recored everyday. Moreover, the pathological of intestinal changes were investigated by HE staining and the level of intestinal cytokine secretion were dected by ELISA assay. The number of salmonella in liver and spleen were also tested.The results showed that 34 LAB strains were isolated from silage and yogurt,which were identified as 10 species namely:L. brevis?L.kefiri? L.parabuchneri?L.farciminis?L.mudanjiangensis?L.mudanjiangensis? L.coryniformis?L. panther is?L.rhamnosus L.casei. Most isolates were homofermentative species and some were heat- or cold- resistant strains.14 LAB strains were screened with possessing potential probiotic properties. TCP009 ? SXJ30?SXJ32?SXJ29 and TCP027 were administered orally to mice for 6 weeks before infection with salmonella on day 43. The results showed that mice were given 70% and 60% survival rates against salmonella infection when fed SXJ30 and SXJ29 compared with PBS group respectively. The histology showed the inflammation of intestinal were reduced when administered orally SXJ30 and SXJ29. Both the levels of cytokines and the CFU of salmonella were reduced significantly. And the degree of decline in body weight was alleviated. These results preliminary showed that SXJ30 and SXJ29 have an effect on antagonistic infection of salmonella in mice model.