[Virulence of Listeria welshimeri].

The species L. welshimeri consists of non-pathogenic bacteria. 16 different strains which were characterized biochemically were unable to multiply within adult NMRI mice after injection of a high dose of about 10(7) bacteria. Even macrophage depleted animals, which were obtained by treatment with highmolecular dextran sulfate, could eliminate L. welshimeri. 5 day old baby mice were resistant against L. welshimeri. L. innocua was as avirulent as L. welshimeri, whereas L. monocytogenes was virulent, since these bacteria multiplied in adult animals, killed macrophage depleted adult mice as well as baby mice after injection of low doses.