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Electron microscopic studies on the location of bacterial proliferation in the liver in murine salmonellosis
1Department of Microbiology and Immunology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Abstract:
Highly susceptible inbred male C57BL/6 mice were infected with 2 X 10(7) virulent Salmonella typhimurium by intraperitoneal inoculation. Samples of the liver were removed 2 or 3 days post-infection for examination by electron microscopy. Rapid infiltration of polymorphs and macrophages was observed in the site of infection. Visual evidence is presented to confirm the destruction of salmonellae within these inflammatory phagocytes as previously reported. The proliferation of the pathogens occurred in the extracellular locations of sinusoids and early lesions, and within hepatocytes.
Insights
This study shows virulent Salmonella Typhimurium initially replicates outside cells in mouse liver, before being destroyed by inflammatory phagocytes like macrophages. Pathogen proliferation also occurs within liver cells.
Area of Science:
- Microbiology
- Immunology
- Pathology
Background:
- Salmonella Typhimurium is a significant bacterial pathogen.
- Understanding Salmonella pathogenesis is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the early cellular interactions and replication sites of Salmonella Typhimurium in vivo using electron microscopy.
- To provide visual evidence of bacterial destruction within phagocytes and identify sites of pathogen proliferation.
Main Methods:
- Infection of C57BL/6 mice with virulent Salmonella Typhimurium via intraperitoneal inoculation.
- Liver tissue sampling at 2 and 3 days post-infection.
- Examination of infected liver tissues using electron microscopy.
Main Results:
- Rapid infiltration of polymorphonuclear leukocytes and macrophages into the infection site.
- Confirmation of Salmonella destruction within inflammatory phagocytes.
- Observation of Salmonella proliferation in extracellular locations (sinusoids, early lesions) and intracellularly within hepatocytes.
Conclusions:
- Salmonella Typhimurium exhibits a complex replication strategy, occurring both extracellularly and intracellularly within hepatocytes.
- Inflammatory phagocytes play a key role in controlling Salmonella infection by destroying the bacteria.
- Early host-pathogen interactions involve rapid immune cell recruitment and bacterial clearance mechanisms.