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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL COMMUNITIES AND INTERACTIONS AND THEIR IMPACT ON FOOD SAFETY

Location: Molecular Characterization of Foodborne Pathogens

Title: Inactivation of avirulent pgm+ and delta pgm Yersinia pestis by ultraviolet light (UV-C)

Authors
item Paoli, George
item Sommers, Christopher
item Scullen, O
item Wijey, Chandi

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2014
Publication Date: June 1, 2014
Citation: Paoli, G., Sommers, C.H., Scullen, O.J., Wijey, C. 2014. Inactivation of avirulent pgm+ and delta pgm Yersinia pestis by ultraviolet light (UV-C). Food Microbiology. DOI:10.1016/j.fm.2014.06.002.

Interpretive Summary: Yersinia pestis is the bacterium that causes bubonic plague. Although it is extremely unusual to acquire plague by eating food, the fact that the bacterium can survive and even grow in some foods, coupled with the potential risk of intentional contamination of foods, makes it a concern for both food safety and food security. Therefore the effectiveness of methods to eliminate this deadly bacterium from foods should be tested. In this study, ultraviolet light, an FDA-approved method for decontamination of food surfaces, was tested to determine its effectiveness in inactivating genetic variants of Yersinia pestis and to determine if the treatment might also reduce the virulence of the surviving bacteria. Ultraviolet light proved to be effective in killing Yersinia pestis. Thus, routine use of this simple and inexpensive technology by the food industry could provide some protection to consumers against this deadly pathogen.

Technical Abstract: Yersinia pestis is the causative agent of bubonic plague. Though not considered a foodborne pathogen, Y. pestis can survive, and even grow, in some foods, and the foodborne route of transmission is not without precedent. As such, concerns exist over the possible intentional contamination of foods with this deadly pathogen. Here we report the inactivation of avirulent (pYV-minus) strains of Y. pestis by ultraviolet light (UV-C, 254 nm). Two strains of Y. pestis containing an intact pgm virulence locus (pgm+) and strains from which the pgm locus was spontaneously deleted (delta pgm) were tested using cells grown in both logarithmic and stationary phase. The D10 values for inactivation (the UV-C dose required to inactivate one log of bacterial cells) of Y. pestis on the surface of agar plates ranged from 0.69 to 1.09 mJ/cm**. A significant difference was observed between the inactivation of cells of Y. pestis strain Yokohama grown in logarithmic and stationary phases, but no significant difference between growth phase sensitivity to UV-C was observed in Y. pestis strain Kuma. No difference in D10 values was observed between pgm+ and delta pgm strains of Yokohama grown to either logarithmic or stationary phase. A measurable difference was observed between the D10 of Kuma pgm+ and Kuma delta pgm grown in logarithmic phase, but this difference was diminished in pgm+ and delta pgm strains of Y. pestis Yokohma. Though strain variations exist, these results suggest that UV-C can inactivate Y. pestis on food surfaces and its routine use in food processing environments could provide some protection to consumers.

Last Modified: 9/1/2014
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