Potential use of continuous cell lines to distinguish between pathogenic and nonpathogenic Listeria spp

Continuous cell lines were tested for their potential use in distinguishing pathogenic from nonpathogenic Listeria species. Listeria monocytogenes and Listeria ivanovii strains were lethal for mice, and culture filtrates were cytotoxic for cultured cells and hemolytic for sheep erythrocytes, while Listeria innocua, Listeria grayi, and Listeria murrayi strains were negative in all three tests. The eight cell lines tested were all affected but varied in sensitivity, with the Chinese hamster ovary cell line being the most sensitive. Cytolytic effect was noted within minutes of the addition of undiluted filtrates, with optimum titers obtained by 24 h.