Survival and Recovery of Salmonella enterica Serovar Typhimurium DT104 at Low Temperature and Water Activity in a Broth System

This study investigated the survival of Salmonella enterica serovar Typhimurium DT104 in a broth system under conditions of low temperature (4°C) and low water activity (a_w, 0.92 to 0.96). Incubation under these conditions resulted in significant reductions in the viability of stationary phase cells, determined by direct plating on selective XLD medium. Reductions in viable numbers were related to injury associated with initial osmotic shock (hyperosmosis) and further injury associated with longer-term storage under the above conditions. Such injured cells were, however, capable of recovering on a nonselective medium (TSA) and contributing to overall viable cell numbers in nonselective post-storage conditions. Storage at more extreme conditions, at lower a_w values, led to cell death at rates influenced by storage temperature. Finally, the data obtained are considered in relation to pathogen survival on the surfaces of beef carcasses during chilling.