Antagonistic effects of bifidobacterium spp. in decrease of cytopathic effects of Verotoxin-producing Escherichia coli

Most Enterohemorrhagic E. coli O157:H7 strains are able to adhere to Vero cell line tightly and produce shiga toxin. The aim of this study was to develop a probiotic in vitro model for protection against E. coli O157:H7.

This study was performed experimentally on probiotic Bifidobacterium and shigatoxinogen E.coli O157:H7 in Vero cell line monolayers. The probiotic bacterium first was grown in MRS media and then was transferred into the vero cell line-containing wells. After incubation, the cells were first exposed to three different treatments (pure stx1, stx2, a mix of stx1and stx2) and then were treated with E. coli O157:H7 bacterial culture. After 24 h incubation at 37° C in CO2 incubator, the cell changes were observed by invert microscope.

The vero cell lines pre-treated with probiotic bacterium responded differently to the doses of used Shiga-toxin and E. coli O157:H7. When the cells were treated with only toxin or E. coli O157:H7, there was a intensive amounts of cell cytotoxicity. However, pre-treatment with prebiotic bacterium decrease significantly the toxicity caused by E. coli O157:H7. The survival rates of the Vero cells treated with probiotic ranged between 80% and 100% compared with controls.  

Based on the results of this study, the probiotic bacteria and the supernatant prepared from their culture decrease the cell toxicity effects of shiga-toxin and E. coli O157:H7. Therefore, the probiotic bacteria can be used as an alive vaccine in food industry in order to prevent and treatment of infections.