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Monocytosis producing activity from virulent and avirulent strains of Listeria
1Department of Microbiology and Immunology, University of Western Ontario, London, Canada.
Abstract:
Monocytosis is a hallmark of listeriosis in many species. A similar phenomenon is induced by a monocytosis-producing activity (MPA) purified from the organism. The relationship between MPA production and virulence is unclear. The purpose of this study was to measure MPA in extracts prepared from strains with known degrees of virulence and haemolysin production. Differential leukocyte counts on peripheral blood cells were performed 24, 48 and 72 h after injection of 0.5 mg MPA. In the strains we tested those known to be virulent produced monocytosis; those which were avirulent did not.
Insights
Virulent Listeria strains produce monocytosis-producing activity (MPA), a key factor in listeriosis. Avirulent strains lack MPA, indicating its role in disease development and monocytosis.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Monocytosis is a characteristic feature of listeriosis across various species.
- A purified monocytosis-producing activity (MPA) from Listeria can induce similar effects.
- The direct link between MPA production and Listeria virulence remains incompletely understood.
Purpose of the Study:
- To quantify MPA levels in Listeria extracts from strains with varying virulence.
- To investigate the correlation between MPA production, virulence, and haemolysin activity.
Main Methods:
- Extraction of MPA from Listeria strains of known virulence.
- Differential leukocyte counts in peripheral blood cells.
- Analysis at 24, 48, and 72 hours post-MPA injection.
Main Results:
- Virulent Listeria strains consistently produced monocytosis upon MPA injection.
- Avirulent Listeria strains did not induce monocytosis.
- MPA levels correlated with the virulence of the tested strains.
Conclusions:
- MPA production is a significant indicator of Listeria virulence.
- MPA plays a crucial role in the development of monocytosis during listeriosis.
- This study clarifies the relationship between MPA and disease pathogenesis.