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Title: USE OF A/J MICE AS A MURINE MODEL FOR I.G. INFECTION WITH LISTERIA MONOCYTOGENES GROWN ON READY-TO-EAT MEAT PRODUCTS

Author
item FAITH, N. - UNIV. OF WISCONSIN
item Luchansky, John
item STEINBERG, H. - UNIV. OF WISCONSIN
item CZUPRYNSKI, C. - UNIV. OF WISCONSIN

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2003
Publication Date: 5/18/2003
Citation: Faith, N.G., Luchansky, J.B., Steinberg, H., Czuprynski, C.J. 2003. Use of a/j mice as a murine model for i.g. infection with listeria monocytogenes grown on ready-to-eat meat products. American Society for Microbiology. Abstract #P-13, p. 509.

Interpretive Summary:

Technical Abstract: Mice are generally considered to be resistant to g.i. infection with Listeria monocytogenes. Previous studies suggested that A/J mice were relatively susceptible to parenteral challenge with L. monocytogenes. In the present study, we determined whether that was also true for intragastric challenge. A/J, ICR and C57BL/6 strains of mice were inoculated i.g. with L. monocytogenes ScottA (serotype 4b). A/J mice were the most susceptible, followed by ICR, while C57BL/6 mice were comparatively resistant. A/J mice, therefore, were chosen for studies of whether growth of L. monocytogenes on ready-to-eat (RTE) meat products (i.e. turkey slices and wieners) affected its virulence when inoculated via the g.i. tract. Inoculation of mice with a slurry of Listeria-contaminated wieners caused a lower level infection than did L. monocytogenes grown in BHI broth. Furthermore, L. monocytogenes failed to multiply when inoculated into packages of wieners, presumably because of the presence of sodium lactate/diacetate. As a result, we switched our focus to smoked turkey cold cuts produced without these additives. L. monocytogenes multiplied from 10(3) to 10(7) CFU per ml fluid in the packages of smoked turkey slices over a 5-day period when incubated at 15°C. Although there were no differences in the number of deaths, the CFU of Listeria monocytogenes recovered from organ homogenates (spleen, liver) were somewhat higher, and there were physical signs of persistent illness (beyond 7 days) in the mice inoculated with L. monocytogenes grown on turkey slices as compared to BHI broth. This is interesting because the time between ingestion of a L. monocytogenes-contaminated food product, and onset of clinical illness, can be several weeks. Our ongoing efforts include investigating additional strains of L. monocytogenes to gain a better understanding of how the environmental signals provided during growth on a RTE meat product (i.e. turkey slices) influence the expression of virulence by L. monocytogenes.