The goal of the current work is to determine the role of the TNF-alpha on the activation of the bacterial growth in an in vivo system. In order to reach this goal we studied the dynamics of the reproduction of vegetative forms of Salmonella and the recultivation of non-cultivating forms of Salmonella in infected animals. Experiments have been conducted both on animals that had been injected with exogenous TNF together with bacterial suspension and on animals that had been exposed to gamma-radiation before infection, since it is known that irradiation increases the secretion of TNF. We demonstrate that in all cases the increase in the level of TNF-alpha in animals leads to the activation of the Salmonella growth. Moreover, in this paper we present the data obtained by the method of molecular display on the identification of genes that are highly expressed in the Salmonella cells cultivated in vitro in the presence of TNF.