Pathogenicity of Listeria monocytogenes in comparison to other Listeria species

In different mouse models the pathogenicity of various strains of Listeria monocytogenes and of other Listeria spp. was evaluated. Although quantitative differences of virulence among strains of L. monocytogenes are found, all isolates have to be regarded pathogenic unless essential virulence factors, such as protein composition of the cell wall or hemolysin production, are lacking. Besides L. monocytogenes, only Listeria ivanovii is able to multiply in the murine host, though definitely to a lesser extent. The other Listeria spp., such as Listeria innocua, Listeria welshimeri and Listeria seeligeri, have to be regarded as non-pathogenic.