title: Survival of Salmonella enterica serotype Tennessee during simulated gastric passage is improved by low water activity and high fat content.
abstract: The low water activity (a(w) 0.3) of peanut butter prohibits the growth of Salmonella in a product; however, illnesses are reported from peanut butter contaminated with very small doses, suggesting the food matrix itself influences the infectious dose of Salmonella,  potentially by improving Salmonella's survival in the gastrointestinal tract. The purpose of our study was to quantify the survival of a peanut butter outbreak-associated strain of Salmonella enterica serotype Tennessee when inoculated into peanut butters with different  fat contents and a(w) (high fat, high a(w); high fat, low a(w); low fat, high a(w); low fat, low a(w)) and then challenged with a simulated gastrointestinal system. Exposures to increased fat content and decreased a(w) both were associated  with a protective effect on the survival of Salmonella Tennessee in the simulated gastric fluid compared with control cells. After a simulated intestinal phase, the populations of Salmonella Tennessee in the control and low-fat formulations were not significantly different; however,  a 2-log CFU/g increase occurred in high-fat formulations. This study demonstrates that cross-protection from low-a(w) stress and the presence of high fat results in improved survival in the low pH of the stomach. The potential for interaction of food matrix and stress adaptations  could influence the virulence of Salmonella and should be considered for risk analysis.
authors: Department of Food Science and Technology, Food Science Building (0418), Duck Pond Drive, Virginia Tech, Blacksburg, VA 24060, USA.
authors: Bryan
authors: B
authors: Aviles
authors: Courtney
authors: C
authors: Klotz
authors: Twyla
authors: T
authors: Smith
authors: Robert
authors: R
authors: Williams
authors: Monica
authors: M
authors: Ponder
mesh_terms: D010367:Arachis / Q000382:microbiology*; D015169:Colony Count, Microbial; D004041:Dietary Fats / Q000378:metabolism*; D004196:Disease Outbreaks; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D050296:Microbial Viability; D008954:Models, Biological; D012478:Salmonella Food Poisoning / Q000517:prevention & control; D019779:Salmonella enterica / Q000254:growth & development*; D013714:Tennessee; D014867:Water / Q000378:metabolism*
chemical_list: D004041:Dietary Fats; D014867:Water