Purpose: In this study, we compared the survival of Salmonella and E. coli O157:H7 isolates from different origins in commercial cookie dough.
Methods: Cookie dough samples were divided into six groups and inoculated with approximately 6.0 log CFU/g of Salmonella isolated from peanut outbreak, egg contaminate, and clinical samples, and E. coli O157:H7 isolated from cookie dough outbreak, salami, and environmental samples, separately. Cell count of each isolate was obtained during eight weeks of storage at 4°C.
Results: Overall, 0.84 to 1.30 log CFU/g reduction and 0.48 to 0.87 log CFU/g reduction was observed for Salmonella and E. coli O157:H7 in cookie dough during eight weeks of storage, respectively. Notably, Salmonella Tennessee isolate from peanut outbreak had much lower viable cell count than Salmonella Enteritidis isolates from eggs and clinical samples (P<0.05) after five days observation. Also, E. coli O157:H7 isolate from the cookie dough outbreak had a significantly lower number of viable cells than other E. coli O157:H7 isolates from salami and environmental samples (P<0.05) during eight weeks storage.
Significance: Our data suggests that Salmonella and E. coli O157:H7, once introduced, remain viable in cookie dough for at least two months. The survival of pathogens is affected by the origins of the isolates. Understanding the factors contributing to such phenomenon will be essential for the control of these pathogens in cookie dough.