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Pathogenicity of Listeria monocytogenes isolates in immunocompromised mice in relation to listeriolysin production
M Tabouret1, J De Rycke, A Audurier
1Institut National de la Recherche Agronomique, Station de Pathologie de la Reproduction, Nouzilly, France.
Abstract:
The virulence of 74 Listeria monocytogenes isolates from clinical cases and food products and of 11 isolates of other Listeria species was tested in mice immunocompromised with carrageenan. Isolates of species other than L. monocytogenes were not lethal to such mice. All 29 clinical isolates of L. monocytogenes (serotypes 1/2a, 1/2b, 4b) and 33 of 42 isolates of various serotypes isolated mainly from dairy products killed all test mice (100% lethality) at an inoculum of 10(4) cfu/mouse. All lethal strains of L. monocytogenes were haemolytic and possessed the 58-Kda band specific for listeriolysin O as demonstrated by SDS-PAGE immunoblotting. The nine avirulent strains of L. monocytogenes had detectable haemolytic activity, but in six of them this activity was significantly weaker than in virulent strains and the 58-Kda band was not detected. The other three avirulent strains were highly haemolytic and possessed the 58-Kda band, which suggests that other factor(s) could be involved in the virulence of L. monocytogenes.
Insights
Virulent Listeria monocytogenes strains, isolated from clinical and food sources, caused 100% lethality in immunocompromised mice. Haemolysin O (hly) and its 58-kDa band were associated with virulence, though other factors may contribute.
Area of Science:
- Microbiology
- Food Safety
- Infectious Diseases
Background:
- Listeria monocytogenes is a significant foodborne pathogen.
- Understanding the virulence factors of L. monocytogenes is crucial for public health.
Purpose of the Study:
- To assess the virulence of Listeria isolates in a mouse model.
- To investigate the role of haemolysin O in L. monocytogenes virulence.
Main Methods:
- Testing 74 L. monocytogenes and 11 other Listeria species isolates in carrageenan-treated mice.
- Assessing lethality at an inoculum of 10(4) cfu/mouse.
- Utilizing SDS-PAGE immunoblotting to detect the 58-kDa band specific for listeriolysin O.
Main Results:
- Non-monocytogenes Listeria species were non-lethal.
- Clinical and foodborne L. monocytogenes isolates demonstrated high lethality (100%).
- Virulent strains possessed haemolytic activity and the 58-kDa listeriolysin O band; some avirulent strains also showed high haemolysis, suggesting additional virulence factors.
Conclusions:
- Listeria monocytogenes exhibits significant virulence in immunocompromised mice.
- Listeriolysin O is a key virulence factor, but not the sole determinant.
- Further research is needed to identify other factors contributing to L. monocytogenes pathogenesis.