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Differing resistance to polymorphonuclear cells of halophilic- and hypotonic-types of Vibrio vulnificus
Abstract:
Bacterial growth and lethality of 4 strains of Vibrio vulnificus infection of mice were enhanced by gamma-irradiation but not by treatment with carrageenan. Therefore, protection against V. vulnificus, at least in the early phases, probably depends mainly on polymorphonuclear cells (PMN), since carrageenan depletes macrophages but not PMN. PMN dependent protection against infection differs for 2 types of V. vulnificus strains. Halophilic- and hypotonic-type were distinguished from the corresponding parent strain. The hypotonic-type of the strains had capsular materials, as clarified by electron microscopic observation of the organisms stained with ruthenium red. On the other hand, halophilic-types either had no observable capsular materials, or incomplete materials, in contrast to the corresponding hypotonic-type. The corresponding halophilic- and hypotonic-types of the strains were compared for virulence in mice. The strains with capsular materials acquired resistance to phagocytic activity and were highly lethal. Capsular materials of V. vulnificus are no doubt important for the expression of virulence.
Insights
Gamma-irradiation enhanced Vibrio vulnificus (V. vulnificus) growth and lethality in mice. Protection against early V. vulnificus infection relies on polymorphonuclear cells (PMN), particularly against strains with capsular materials.
Area of Science:
- Microbiology
- Immunology
- Pathogen Virulence
Background:
- Vibrio vulnificus (V. vulnificus) is a significant marine pathogen.
- Understanding host-pathogen interactions is crucial for developing effective treatments.
- The role of bacterial structures in V. vulnificus virulence requires further investigation.
Purpose of the Study:
- To investigate the impact of gamma-irradiation and carrageenan on V. vulnificus infection in mice.
- To elucidate the role of polymorphonuclear cells (PMN) and macrophages in V. vulnificus protection.
- To compare the virulence of different V. vulnificus strains, focusing on capsular material expression.
Main Methods:
- Infection models using mice challenged with V. vulnificus strains.
- Treatment with gamma-irradiation and carrageenan to modulate host immune response.
- Electron microscopy with ruthenium red staining to visualize bacterial capsular materials.
- Assessment of bacterial growth, lethality, and phagocytic activity.
Main Results:
- Gamma-irradiation enhanced bacterial growth and lethality, while carrageenan did not.
- Protection against early V. vulnificus infection primarily depends on PMN, not macrophages.
- Two distinct V. vulnificus strain types were identified: hypotonic-type with capsular materials and halophilic-type with limited or no capsular materials.
- Strains possessing capsular materials exhibited increased resistance to phagocytosis and higher lethality.
Conclusions:
- Capsular materials are critical for V. vulnificus virulence and resistance to host defenses.
- PMN play a key role in early-stage protection against V. vulnificus infection.
- Gamma-irradiation may exacerbate V. vulnificus infections, warranting caution.