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United States Department of Agriculture

Agricultural Research Service

Title: Inhibition of Shigella Sonnei by Ultraviolet Energy on Agar, Liquid Media and Fresh Produce

Author
item Rajkowski, Kathleen

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 16, 2006
Publication Date: May 1, 2007
Citation: Rajkowski, K.T. 2007. INHIBITION OF SHIGELLA SONNEI BY ULTRAVIOLET ENERGY ON AGAR, LIQUID MEDIA AND FRESH PRODUCE. Journal of Food Safety. 233-240.

Interpretive Summary: Ultraviolet light (UV) at a wave length of 254 nm is used to kill bacterial pathogens on surfaces. In addition to this UV wave length, another light source at 185 nm is also effective. The combination of both light sources was used to determine the reduction of Shigella sonnei, a bacterial pathogen, in liquids and on agar and fresh produce surfaces. The combination UV light was effective in killing this pathogen on the agar surface. However, higher doses were required to kill the pathogen in the liquid. Because of the uneven produce surface, no reduction was observed until the UV treatment was combined with a 0.1 % hygrogen peroxide wash. The combination resulted in an one-hundred to one-thousand folds reduction of the pathogen. The two light sources were effective in providing a means of sanitizing food surfaces and liquids. The combination of the disinfectant and UV treatment will reduce pathogen levels on produce. This data can be used by processors to ensure microbiological safety of produce and thereby, reducing foodborne illness outbreaks associated with produce.

Technical Abstract: The germicidal effect of ultraviolet light (UVC) at 254 nm is used to decontaminate surfaces. Using the combined light from a 185 and 254 nm source, the reduction of Shigella sonnei was determined on inoculated agars and radish sprouts, and in distilled water and vegetable broth. The combined UVC lights were very effective in reducing the number of S. sonnei on inoculated agar surfaces at a dose of 2040 uW-sec-cm2, resulting in >8 log reduction. The reduction in the liquid samples reached >5 log at 3400 uW-sec-cm2. Due to the unevenness of the radish sprouts, a 2-3 log reduction was achieved only when combined with a H2O2 wash treatment. The combined light sources were effective in killing the S. sonnei on agar and in liquids, which can provide pathogen free surfaces and water.

Last Modified: 12/18/2014