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Estimate and compare the pathogenicity and virulence of a panel of L. monocytogenes strains; the panel includes six strains tested in ongoing monkey clinical trials and two additional isolates from the ongoing ARS/FSIS hot dog study; screen the panel of L. monocytogenes strains for
mouse pathogenicity, mouse lethality dose and invasion of the liver and spleen. Study will provide risk assessors more scientific information to assist in interpretation of data for development of dose-reponse model for human listeriosis.
Screen a panel of L. monocytogenes strains for pathogenicity in the mouse, and for those which are found to be pathogenic, to determine the lethal dose and infectivity in the mouse. Six strains of L. monocytogenes were previously used in a primate study. In the first phase, strains will be injected intraperitoneally into immunocompromised mice. Isolated which case death within five days will be designated as pathogenic. Second phase the lethal dose will be measured in immunocompromised mice, and calculated according to the method of Reed and Muench. Third phase, mouse pathogenic strains will be injected intraperitoneally into mice and the bacteria enumerated in livers and spleen. <p>
In addition, pulsed field gel electrophoresis (PFGE) patterns of tissue isolates will be compared with the panel strains to determine the stability of the panel strains during passage through the mouse. Information obtained will extend the information obtained from previous monkey model studies and its application for L. monocytogenes risk assessment for humans.