Summary of Awards to Date

Contamination of fruits, nuts, and vegetables by filamentous Salmonella; persistence and virulence.

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Feb. 1, 2010 - Jan. 31, 2013

Award Number


Funding Agency

Center for Produce Safety

Amount Awarded



Charles W. Kaspar, Ph.D.
University of Wisconsin-Madison


Wong, A., and Czuprynski, C.


Recent outbreaks associated with nuts, peanut butter, toasted oats, and vegetables in the U. S. have increased concerns of Salmonella contamination, survival, and infectivity in or on products with reduced water activity. These products may become contaminated with Salmonella at one or more stages of pre-harvest, harvest, processing, or storage. The organism does not normally grow in low-moisture environments but some serovars can survive for prolonged periods. Salmonella encounters a myriad of stressful conditions in the food production chain that can trigger specific and general stress-protection systems that render cells more tolerant to stress and promote persistence in the environment or food. One interesting response to stress is the formation of filaments that can reach >100 I?m in length. Much of the basic biology of filamentation is unknown including triggers, production on foods, survival characteristics, and virulence. The formation of Salmonella filaments is significant to food safety because under favorable conditions the filaments will form septa and divide the filament into multiple, typical cells that can impact estimations of pathogen numbers, the effectiveness of intervention practices (i.e., critical control points), and risk assessments. This proposal will study Stress-Induced Filamentous Salmonella (SIFS) on fruits, nuts, and vegetables and specifically determine there: 1.) pathogen load assessments and persistence on foods, 2) formation and characterization, 3) mitigation measures, 4) infectious dose and virulence. This project will provide fundamental information on stress response in Salmonella that impacts persistence on fruits, nuts, and vegetables and define effective harvest and/or production practices that prevent formation or inactivate these stress-induced cells.