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Plasmid-associated virulence of Salmonella enteritidis
M Hovi1, S Sukupolvi, M F Edwards
1National Public Health Institute, Helsinki, Finland.
Abstract:
Plasmid-associated virulence of Salmonella enteritidis was studied using plasmid-cured and plasmid-reintroduced strains. The plasmidless strain was unable to grow in the liver of mice after intravenous inoculation. Reintroduction of the plasmid pEX106 from the original S. enteritidis fully restored its capacity to grow in the mice. The plasmid pEX102 of Salmonella typhimurium introduced into the plasmid-cured S. enteritidis had a similar effect. The smooth lipopolysaccharide character of the S. enteritidis strains was not affected by the presence or absence of the plasmid, and the same was true of their high resistance to complement in guinea-pig serum as such or with added antibody.
Insights
Salmonella enteritidis virulence is linked to plasmids. Restoring plasmids to a cured strain restored its ability to grow in mice, demonstrating plasmid importance for Salmonella growth and survival.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Plasmids are extrachromosomal DNA elements that can carry virulence factors in bacteria.
- The role of plasmids in the virulence of Salmonella enteritidis, a significant foodborne pathogen, requires further elucidation.
Purpose of the Study:
- To investigate the contribution of plasmids to the virulence of Salmonella enteritidis.
- To determine if specific plasmids are essential for Salmonella enteritidis to colonize and grow within a host environment.
Main Methods:
- Construction and characterization of plasmid-cured and plasmid-reintroduced Salmonella enteritidis strains.
- Intravenous inoculation of mice with different Salmonella strains to assess liver colonization and growth.
- Evaluation of lipopolysaccharide (LPS) character and serum resistance in relation to plasmid presence.
Main Results:
- The plasmidless Salmonella enteritidis strain exhibited significantly reduced ability to grow in the mouse liver post-inoculation.
- Reintroduction of the native plasmid (pEX106) or a heterologous plasmid (pEX102 from Salmonella typhimurium) fully restored the in vivo growth capacity.
- Plasmid presence or absence did not alter the smooth lipopolysaccharide phenotype or high resistance to complement-mediated killing.
Conclusions:
- Plasmids play a critical role in the virulence of Salmonella enteritidis, specifically in enabling growth within the host liver.
- The presence of specific plasmids is essential for Salmonella enteritidis to establish infection and colonize host tissues effectively.