Epidemiologic Attributes and Virulence Profile of Salmonella Tennessee isolates from Infections associated with Peanut Butter National Outbreak

Abstract

The multi-state outbreak of Salmonella serotype Tennessee infections associated with peanut butter during 2006-2007 was the first outbreak in the United States associated with this food vehicle.  We investigated whether the outbreak-related strains had any distinct virulence attributes. We have analyzed 96 representative isolates from human and non-human sources from multiple states for attachment and invasion of caco-2 cell. In logistic regression analysis, we found that Salmonella Tennessee strains associated with the peanut butter outbreak were more likely to be highly invasive than strains from non-outbreak sources, OR 4.03 (95% CI 1.42, 11.41). Results from this study suggest that peanut butter could have provided an impetus for the expression of certain sets of virulence genes leading to the observed high level of invasiveness of the Salmonella Tennessee contaminants.  The occurrence of this outbreak underscores the importance of hygienic practices in peanut butter manufacturing plants for the prevention of such mass contamination.

Keywords: Salmonella Tennessee; peanut butter; newly emerging food vehicles for Salmonella; risk factors for Salmonella Tennessee