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Cytotoxicity of extracellular Legionella pneumophila
1Department of Microbiology, University of Iowa, Iowa City 52242.
Abstract:
Legionella pneumophila, the causative agent of Legionnaire's disease and Pontiac fever, is known to produce a cytopathic effect on macrophages. The capacity of extracellular L. pneumophila to mediate toxicity for guinea pig peritoneal macrophages and J774 mouse macrophages was assessed. Extracellular organisms were found to be capable of mediating toxicity; however, toxic activity appeared to require close proximity with the mononuclear cell surface. Serogroup 1 strains grown on supplemented Mueller-Hinton agar exhibited variable expression of toxic activity. One strain positive on supplemented Mueller-Hinton agar was cytotoxic and unable to replicate in J774 macrophages but remained virulent for guinea pigs at high doses.
Insights
Extracellular Legionella pneumophila can harm macrophages, but needs to be close to the cell surface. Some strains show variable toxicity, impacting virulence and replication.
Area of Science:
- Microbiology
- Immunology
- Pathogen-host interactions
Background:
- Legionella pneumophila causes Legionnaires' disease and Pontiac fever.
- L. pneumophila is known to damage macrophages, a key component of the immune system.
Purpose of the Study:
- To investigate the toxicity of extracellular L. pneumophila on macrophages.
- To determine the conditions required for L. pneumophila-mediated macrophage toxicity.
Main Methods:
- Assessed the cytotoxic effects of extracellular L. pneumophila on guinea pig peritoneal macrophages and J774 mouse macrophages.
- Evaluated the role of proximity to the mononuclear cell surface in mediating toxicity.
- Examined the variable expression of toxic activity in Serogroup 1 strains grown on supplemented Mueller-Hinton agar.
Main Results:
- Extracellular L. pneumophila demonstrated toxicity towards macrophages.
- Toxic activity was dependent on close proximity to the mononuclear cell surface.
- Serogroup 1 strains displayed varied toxic activity expression.
- One strain was cytotoxic and failed to replicate in J774 macrophages, yet retained virulence in guinea pigs.
Conclusions:
- Extracellular L. pneumophila can induce macrophage toxicity, contingent on cell surface proximity.
- Variability in toxic activity exists among L. pneumophila strains, influencing host-pathogen interactions.
- Certain cytotoxic strains may maintain virulence despite impaired replication in specific macrophage models.