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Updated: Oct 9, 2026
Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages
Published on: October 25, 2017
Effect of constitutively expressed phoP gene on the localization of Salmonella typhimurium within Mac-1 positive
H Matsui1, M Eguchi, Y Kikuchi
1Center for Basic Research, The Kitasato Institute, Tokyo, Japan. matsui-h@kitasato.or.jp
Abstract:
Intracellular localization of the wild-type (Spv+), the phoP-constitutively expressed strain (PhoPc), and the spv-deleted strain (Spv-) of Salmonella typhimurium was examined by the use of confocal laser scanning microscopy analysis of immunostained sections of mouse spleens after oral or subcutaneous inoculation. Only 40% of salmonellae of both the PhoPc and the Spv- strains were detected intracellularly within Mac-1 positive cells at day five after oral or day four after subcutaneous inoculation. In contrast, over 85% of salmonellae of the Spv+ strain were detected inside Mac-1 positive cells. In both inoculation trials, the splenic colony-forming unit values for the PhoPc and Spv- strains were significantly lower than the corresponding value for the Spv+ strain. These findings suggest that the constitutively expressed phoP gene of S. typhimurium attenuated virulence by limiting intracellular proliferation within mouse spleen phagocytes, and that the lack of spv genes had the same effect.
Insights
Salmonella typhimurium strains with a constitutively expressed phoP gene or deleted spv genes showed limited intracellular proliferation in mouse spleen phagocytes. This suggests attenuated virulence for both genetic modifications in Salmonella infection.
Area of Science:
- Microbiology
- Immunology
- Pathogen Biology
Background:
- Salmonella typhimurium virulence is influenced by specific genes.
- Intracellular survival within host cells is crucial for Salmonella pathogenesis.
Purpose of the Study:
- To investigate the intracellular localization and proliferation of wild-type, phoP-constitutively expressed, and spv-deleted Salmonella typhimurium strains.
- To determine the role of phoP and spv genes in Salmonella typhimurium's intracellular survival within mouse spleen.
Main Methods:
- Confocal laser scanning microscopy was used to analyze immunostained sections of mouse spleens.
- Salmonella typhimurium strains (wild-type, PhoPc, Spv-) were inoculated orally or subcutaneously into mice.
- Intracellular localization within Mac-1 positive cells and splenic colony-forming units were quantified.
Main Results:
- Over 85% of wild-type Salmonella typhimurium (Spv+) were found intracellularly, compared to only 40% for PhoPc and Spv- strains.
- Splenic colony-forming unit values were significantly lower for PhoPc and Spv- strains than for the Spv+ strain.
- Intracellular proliferation was limited in PhoPc and Spv- strains within mouse spleen phagocytes.
Conclusions:
- Constitutive expression of the phoP gene attenuates Salmonella typhimurium virulence by limiting intracellular proliferation.
- Deletion of spv genes also attenuates Salmonella typhimurium virulence, mirroring the effect of phoP modulation.
- Both phoP and spv genes play critical roles in Salmonella typhimurium's ability to proliferate intracellularly within host phagocytes.
