Enhanced recovery of Salmonella Typhimurium DT104 from exposure to stress at low temperature

Salmonella enterica serovar Typhimurium (S. Typhimurium) remains an important cause of food-borne infection in the developed world. In order to establish infection within a host, Salmonella must survive and recover from a range of environmental stresses. S. Typhimurium strain SL1344 is among the most extensively studied pathogenic Salmonella strains, while S. Typhimurium phage type DT104 is an important type that has been associated with pandemic spread and a high number of food-borne disease outbreaks over the last two decades. In this study, we have compared the abilities of these two S. Typhimurium types to recover from stress exposures commonly encountered in food production, including 685 mM NaCl, pH 3.8, low temperature (6 6C) and combinations thereof. Following removal from prolonged (8 days) stress, DT104 cultures that had been exposed to low temperature, with or without additional stress, resumed exponential growth more rapidly than SL1344 cultures exposed to the same conditions. SL1344 showed higher levels of filamentation than DT104 in response to NaCl exposure at low temperature. Further, SL1344 incurred higher levels of membrane damage in response to elevated NaCl and pH 3.8 at both temperatures compared with DT104. However, both strains recovered normal cell division and membrane integrity within 6 h when all stresses were removed