Abstract:  Some Clostidium could regulate the development of the host immune system. Hence， these Clostidium strains had the potential to be used as probiotics. Since the population of Clostridium in chicken cecal contents was relative high， the aims of this study were to isolate functional Clostidium strains from chicken cecal contents and subsequently study their protective effect against Salmonella infection. In this study， a Gram\|positive filamentous Clostridium sp C1 which could transfer daidzein to equol， was isolated from chicken cecal contents and then the animal experiments were conducted to study the protective effect of Clostridium sp C1 on Salmonella infection. As the tetracycline treated group did， the Clostridium sp C1 also had effect on decreasing the number of Salmonella in cecal contents and promoting the growth of chicken. Thus， the Clostridium sp C1 had the potential to be used as a tetracycline substitute. Although， the high concentration of S-equol （5 mg·mL-1） had the function on inhibiting the growth of Salmonella in vitro and the Clostridium sp C1 had the function of transfering daidzein to S-equol， the inhibition effects of Clostridium sp C1 on Samonella growth was not observed in vitro. The probiotic mechanism of Clostridium sp C1 need to be further studied.

Key words: Clostridium, equol, chicken, Salmonella