ARS | Publication request: Virulence of Listeria monocytogenes following repeated exposure to Ultraviolet (254nm) Light

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2008
Publication Date: July 2, 2008
Citation: Sommers, C. 2008. Virulence of Listeria Monocytogenes following repeated exposure to ultravioet light [abstract]. Institute of Food Technologists Annual Meeting. New Orleans, LA. p.1.

Technical Abstract: The foodborne pathogen Listeria monocytogenes is an occasional contaminant of ready-to-eat meat products such as frankfurters. Frankfurters can be contaminated following cooking and prior to packaging by contact with contaminated surfaces such as conveyors and packaging equipment. Ultraviolet Light (UV) (254 nm) is an FDA approved technology that can inactivate pathogenic bacteria on food contact surfaces. In this study L. monocytogenes H7762 was inoculated onto stainless steel coupons and exposed to 100 mJ UV Light, resulting in inactivation of greater than 6 log of the pathogen. Twelve surviving isolates were then selected and separately subjected to a total of ten rounds of propagation and exposure to UV Light. The 12 individual isolates were tested for their resistance to UV Light and their ability to invade human cells. The UV resistance of the UV treated L. monocytogenes was significantly greater than the non-UV treated H7762 parent. However, while more UV resistant, 10 of the 12 isolates were unable to invade a human colon tumor (RKO) cell line. The twelve UV treated clones also displayed variable phospholipase and hemolysin virulence phenotypes through plating on chromogenic and horse blood agar plates. While repeated exposure to UV Light (254 nm) resulted in increased resistance of L. monocytogenes to that intervention technology, the surviving L. monocytogenes were attenuated as a result of the repeated UV treatment.