[Factors of Salmonella typhi virulence in relation to the development of new vaccines].

Although many vaccines against typhoid fever have been developed, none have been adapted for their further application on developing countries. In order to get better vaccines, the virulence factors of both S. typhi and S. typhimurium have been studied. Thus, some protection assays have been made using surface antigens involved on virulence or using live attenuated vaccines of bacteria mutated on virulence genes. Here we present a brief review about virulence factors studied so far for the development of new vaccines.