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Intracellular destruction of salmonellae in genetically resistant mice
1Department of Microbiology and Immunology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Abstract:
Virulent Salmonella typhimurium, 2000 LD50, were injected intraperitoneally into inbred male A/J mice, genetically resistant to salmonella infection. Peritoneal exudate cells were harvested between 5 and 54 h after infection and examined by electronmicroscopy. Polymorphs were seen ingesting as well as digesting the pathogens as early as 5 h after infection. Macrophages were equally active in destroying the phagocytosed organisms throughout this period. In the meantime, the proliferation of salmonellae appeared to occur extracellularly in the peritoneal cavity as evidenced by their division.
Insights
Infection-resistant mice show immune cells actively destroying Salmonella typhimurium. Despite this, the bacteria proliferate extracellularly in the peritoneal cavity.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Salmonella typhimurium is a significant bacterial pathogen.
- Inbred male A/J mice are genetically resistant to Salmonella infection.
- Understanding the host-pathogen interaction in resistant models is crucial for immunology research.
Purpose of the Study:
- To investigate the cellular response to Salmonella typhimurium infection in genetically resistant mice.
- To examine the phagocytic and digestive capabilities of peritoneal exudate cells.
- To observe the in vivo behavior and proliferation of Salmonella typhimurium.
Main Methods:
- Intraperitoneal injection of virulent Salmonella typhimurium (2000 LD50) into A/J mice.
- Harvesting of peritoneal exudate cells at various time points (5-54 h post-infection).
- Examination of cells and bacteria using electron microscopy.
Main Results:
- Polymorphonuclear leukocytes (PMNs) were observed actively ingesting and digesting Salmonella typhimurium as early as 5 hours post-infection.
- Macrophages demonstrated sustained activity in phagocytosing and destroying the bacteria throughout the observation period.
- Evidence of extracellular bacterial division, indicating proliferation within the peritoneal cavity, was observed.
Conclusions:
- Genetically resistant mice mount a robust phagocytic response against Salmonella typhimurium via PMNs and macrophages.
- Despite effective phagocytosis, Salmonella typhimurium can proliferate extracellularly in the peritoneal cavity of resistant hosts.
- This study highlights a complex interplay between host resistance mechanisms and bacterial survival strategies.