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Mucin allows survival of Salmonella typhi within mouse peritoneal macrophages
J Sein1, V Cachicas, M I Becker
1Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago.
Abstract:
Salmonella typhi is a facultative intracellular human specific pathogen. Both immunocompetent and immunodeficient mice are resistant to S. typhi. However, when they are infected with S. typhi suspended in mucin, the bacteria become pathogenic and infect peritoneal phagocytic cells. The LD50 for mice was 10(5) bacteria suspended in 5% mucin; mouse survival was approximately 48 hours after injection. A high number of bacteria was recovered from peritoneal cells; transmission electron microscopy disclosed a large number of vesicles filled with S. typhi cells in peritoneal cells from infected animals. The addition of mucin to cultures of the reticuloendothelial cell line J774.3 also allowed invasion of the mammalian cells with S. typhi. These data indicate that mucin allows intracellular survival of S. typhi.
Insights
Mucin enables Salmonella typhi, a human pathogen, to infect mice by allowing intracellular survival in phagocytic cells. This finding is crucial for understanding Salmonella typhi pathogenesis.
Area of Science:
- Microbiology
- Pathogen Research
- Immunology
Background:
- Salmonella typhi is a human-specific pathogen.
- Mice are generally resistant to Salmonella typhi infections.
- The role of host factors in Salmonella typhi pathogenesis is not fully understood.
Purpose of the Study:
- To investigate the role of mucin in Salmonella typhi pathogenesis.
- To determine if mucin can render mice susceptible to Salmonella typhi infection.
- To elucidate the mechanism by which mucin facilitates Salmonella typhi invasion and survival.
Main Methods:
- Infection of mice with Salmonella typhi suspended in mucin.
- Determination of the lethal dose 50 (LD50) and survival time.
- Recovery of bacteria from peritoneal cells.
- Transmission electron microscopy of infected peritoneal cells.
- Invasion assays using the J774.3 reticuloendothelial cell line.
Main Results:
- Salmonella typhi suspended in mucin became pathogenic in mice, with an LD50 of 10(5) bacteria.
- Infected mice survived approximately 48 hours post-injection.
- High numbers of Salmonella typhi were recovered from peritoneal cells, often within vesicles.
- Mucin facilitated the invasion of Salmonella typhi into J774.3 cells.
Conclusions:
- Mucin plays a critical role in enabling Salmonella typhi to infect mammalian cells.
- The presence of mucin allows for intracellular survival and multiplication of Salmonella typhi.
- These findings suggest mucin as a key factor in Salmonella typhi pathogenesis.