|Kim, S - WSU|
|Bakko, Marlene - WSU|
Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2004
Publication Date: July 1, 2004
Citation: Kim, S.H., Bakko, M., Knowles Jr, D.P., Borucki, M.K. 2004. Oral inoculation of a/j mice detects invasiveness differences between listeria monocytogenes epidemic and environmental strains. Infection and Immunity. 72(7):4318-4321. Interpretive Summary: Listeria monocytogenes is a food-borne pathogen that can cause severe disease in humans and animals. Although L. moncytogenes is widely distributed in nature and commonly isolated from food products, listeriosis is a relatively rare disease. A particular serotype, serotype 4b, is responsible for most epidemics so it is likely that different strains of L. monocytogenes have different degrees of virulence. This paper describes the testing of an in vivo model that may be used to assess the virulence potential of Listeria monocytogenes strains. The mouse model described in this paper was able to differentiate epidemic from environmental strains of L. moncytogenes, with epidemic strains being more invasive and infective than environmental strains.
Technical Abstract: Listeria monocytogenes is a food-borne pathogen that can cause severe disease in humans and animals. Invasion of host tissues is a crucial component of its pathogenesis. The purpose of this study was to test an in vivo model for comparison of the relative invasiveness of epidemic and environmental L. monocytogenes strains. Previous mouse models used intraperitoneal or intravenous inoculation with high numbers of bacteria to assess strain invasiveness. However, these models do not address survival and translocation in the gut. An A/J mouse model using intragastric inoculation was recently described by Czuprynski et al. (2003). This study described the characterization of two strains of L. monocytogenes, however, sodium pentobarbital was used for anesthesia and this was later shown to increase susceptibility to infection. Therefore, it is important to test the efficacy of this model using more strains and a different means of anesthesia. Four-week old A/J mice from Harlan vendor were orally infected with six epidemic and six environmental strains using isoflurane anesthesia. Epidemic strains were significantly more invasive than environmental strains (P < 0.05), and the intestines of some mice infected with epidemic strains had intensive hemorrhage. Mice inoculated with epidemic strains were more likely to become systemically infected as compared to mice inoculated with environmental strains (P < 0.01). There was no significant difference in invasiveness of serotype 4b and non-4b strains. These results indicate that oral infection of Harlan A/J mice with L. monocytogenes may serve as a useful model for investigating invasiveness of L. monocytogenes strains.