Pathogenicity testing of Listeria strains isolated from food in fertilized hen's eggs.

Pathogenicity testing of 10-day-old fertilized hen's eggs infected with Listeria species demonstrated that L. monocytogenes isolated from cheese and human samples caused death in 100% of the injected chicken embryos within 96 h. In contrast, L. innocua isolated from cheese was fatal for only 17% of the infected embryos. All embryos infected with L. seeligeri survived. The results confirmed statements of previous authors about the pathogenicity of L. monocytogenes, regardless of its origin.