Pathogenicity test for Listeria monocytogenes using immunocompromised mice

Abstract

The lethality of Listeria isolates was determined with normal adult mice and mice that were immunocompromised by treatment with 20 mg of carrageenan per kg. The mean 50% lethal doses (LD50s) of the pathogenic isolates were significantly lower (a = 0.05) in' the immunocompromised mice than in the untreated mice, with an average reduction of 5.8 1glo units. Ini contrast, the mean LD50s of the nonpathogenic isolates were lowèr in the immunocompromised mice by an average of only 0.4 loglo unit, a differehce that was not significant (a = 0.05). Whén immunocompromised mice were used, the LD50s of pathogenic Listeria monocytogenes isolates were lower than those of nonpathogenic L. innocua and L. seeligeri isolates by '6 loglo units and lower than those of nonpathogenic L. ivanovii isolates by .-41glo units. Pathogenic L. monocytogenes isolates could be distinguished from nonpathogenic isolates by their ability to cause deaths in immunocompromised mice in 3 days at a dose of-104 CFU per mouse. An alternative procedure using iron-overloaded mice failed to effectively differentiate pathogenic Listeria isolates.

Naturally occurring virulence-attenuated isolates of Listeria monocytogenes capable of inducing long term protection against infection by virulent strains of homologous and heterologous serotypes

“…The mouse bioassay has proved to be an extremely sensitive assay for assessing the pathogenicity of L. monocytogenes. Experiments carried out by Mainou-Fowler et al [11] and Stelma et al [12] demonstrated that virulence of L. monocytogenes for man can be correlated with pathogenicity in mice. In the experiments presented here three strains were discovered, belonging to serotypes 3a and 4a, that showed intermediate levels of replication in target organs of infected mice.…”

DEVELOPMENT OF NEW ENRICHMENT BROTHS AND PLATING AGARS FOR ISOLATION OF HEMOLYTIC SPECIES OF LISTERIA

“…seeligeri also produce hemolysins, but these species have rarely been encountered in human infections. Stelma et al ( 1987) concluded from studies in an immunocompromised mouse model that neither of these species is pathogenic. In contrast, Farber and Speirs (1987) found that a hemolytic strain of L .…”

IMMUNOLOGICAL AND CYTOPATHOGENIC PROPERTIES OF LISTERIA MONOCYTOGENES ISOLATED FROM NATURALLY CONTAMINATED MEATS

“…Pathogenicity testing of Listeria spp. has often been performed by using the FDA approved mouse model (Stelma et al 1987); however, this is not feasible for routine use. As a substitute, use of various tissue culture cell lines have been proposed by several researchers to test the cytopathogenicity of Listeria spp.…”