Background & Objectives: Salmonella is amongst the most important food-borne pathogens and s .typhimurium is the most common species causing food infection. L. casei, B. bifidum and B. angulatum are among probiotics with siginificant benefical effects in consumers. The purpose of this study was to investigate the interaction of the mentioned probiotics with s .typhimurium in vitro and growth in synthetic peptone water medium to evaluate the provisional effects of probiotic consumption in prevention and treatment of s .typhimurium food infection in humans.

  Methods: In order to activate the lyophilized bacteria, they were inoculated in erlene meyer containing peptone water and incubated at 37 ^°C for 24 hours. The activated probiotics and s .typhimurium were then incubated separately and together in peptone water medium for 24 hours at 37 ^° c. Then, the number of their probiotic bacteria and S.typhimurium were counted in MRS and BGA media using surface plate method. This procedure was repeated 10 times for each experiment and a mean number of s .typhimurium in each ml of erlene meyer containing s .typhimurium alone and with probiotics and also the mean number of probiotic bacteria in each ml of erlene meyer containing probiotic alone and with salmonella were compared using independent t-test.

  Results: Co-cultural growth of L.casei and B.angulatum significantly inhibits s .typhimurium growth (P<0.05) but the inhibitory effect of B.bifidum was not meaningful and the co-culture of S.typhimurium had no meaningful effect on the growth of the above bacteria.

  Conclusions: Consumption of products containing L.casei and B.angulatum could have benefical effects in prevention and treatment of S.typhimurium infection although more in vivo researches should be carried out in this regard.