Oct. 1, 2010 - Sep. 30, 2013Award Number
Center for Produce SafetyInvestigator
Amy C. Wong, Ph.D.
University of Wisconsin-Madison
Czuprynski, C., and Kaspar, C.Summary
Salmonella causes an estimated 2-4 million cases of human gastroenteritis per year in the United States. Although most cases resolve in 5-7 days, the very young, elderly, and immunocompromised are susceptible to more severe infections that result in an estimated 500 deaths per year. It has been estimated that 95% of these cases result from consumption of contaminated food. Salmonella encounters myriad stresses in the pre-harvest and processing environments. Desiccation and temperature stress are a few of the commonly encountered stresses. In response, Salmonella triggers stress protection systems that render cells more tolerant to the inducing stress as well as cross protection to other stresses. As a consequence, there is greater survival and prolonged persistence of the organism in the environment or food. One of the long-term goals of our research is to define the role of stress-responses in the dissemination, fitness, and pathogenesis of salmonellae. One interesting response to stress that we and other groups have observed in salmonellae is the formation of filaments (elongated cells without septation) that can be greater than 200 microns long. The underlying processes and purpose of filament formation are unknown, but we have observed filament formation in response to several stresses including; desiccation, temperature, and ultraviolet light. This common response to different stresses points to a central system of importance to persistence and dissemination of this important human pathogen. Key questions center on whether filamentous salmonellae have enhanced survival properties and are infectious. Of equal significance is the formation of septa once encountering favorable conditions that results in a sudden burst in Salmonella numbers. Thus, filaments can affect tests to enumerate Salmonella in a food, which could influence retrospective assessments of the infectious dose and risk assessments. Likewise, the occurrence of filamentous Salmonella in the processing environment may influence the effectiveness of processing parameters. It is critical to understand under what conditions filaments are formed, whether filament formation affects the survival of Salmonella under other stress conditions, and if in turn these changes alter the virulence properties of the Salmonella cells. Our proposed research will provide insights into these important food safety questions.