Survival of Salmonella enterica serotype Tennessee during simulated gastric passage is improved by low water activity and high fat content.

The low water activity (aw 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 aw (high fat, high aw; high fat, low aw; low fat, high aw; low fat, low aw) and then challenged with a simulated gastrointestinal system. Exposures to increased fat content and decreased aw 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 signif...