Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2004
Publication Date: 3/1/2005
Citation: Faith, N.G., Tamplin, M.L., Bayles, D.O., Luchansky, J.B., Czuprynski, C.J. 2005. Effects of suspension in emulsified wiener, or incubation in wiener packages, on the virulence of L. monocytogenes Scott A in intragastrically inoculated A/J mice. Journal of Food Protection. v. 68. p. 597-601. Interpretive Summary: The degree to which contact with food may increase the pathogenicity of Listeria monocytogenes is currently in question. Since outbreaks of listeriosis have been linked to contaminated frankfurters, L. monocytogenes Scott A was placed into contact with frankfurters and held at 15C for 7 days prior to recovery of the pathogens and inoculation of the pathogens into the stomachs of mice. Mice were inoculated with L. monocytogenes homogenized with frankfurters or in fluid recovered from the frankfurter package, and were examined after 3 days to determine the extent of infection. L. monocytogenes that had been in contact with frankfurters was not more virulent than L. monocytogenes grown in brain heart infusion broth, a common laboratory medium used for growing bacteria. This indicates that L. monocytogenes Scott A introduced into the gastrointestinal tract is not more likely to cause a more severe infection as a result of being exposed to frankfurters or by being associated with frankfurter meat.
Technical Abstract: Several outbreaks of listeriosis have been associated with contamination of wieners and other ready-to-eat meat products. In this study we addressed the question of whether emulsification in, or growth on, wieners triggers a response in the listerial cells that makes them more virulent, or protects them against the harsh environment of the gastrointestinal tract in mice. Our results indicate that L. monocytogenes Scott A grows poorly, if at all, in packages of wieners inoculated with 5 x 10(3) to 5 x 10(6) CFU per package and incubated at 15C. Neither mice inoculated with L. monocytogenes Scott A emulsified in a slurry of homogenized wieners, nor recovered from wiener package fluid after a 7-day incubation at 15C, were more virulent when inoculated into the stomachs of A/J mice than L. monocytogenes Scott A grown in BHI broth. These findings suggest that the ability of L. monocytogenes Scott A to cause systemic infection following introduction into the gastrointestinal tract was not improved by incubation with wieners or by being suspended in a meat matrix.