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

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 Listeria monocytogenes Scott A grows poorly, if at all, in one brand of commercially prepared wieners inoculated with 5 × 103 to 5 × 106 CFU per package and incubated at 15°C. Neither L. monocytogenes Scott A emulsified in a slurry of homogenized wieners nor recovered from wiener package fluid after a 7-day incubation at 15°C were more virulent when inoculated into the stomachs of A/J mice than L. monocytogenes Scott A grown in brain heart infusion 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 suspension in a meat matrix.