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Electron microscopic evidence for in vivo extracellular localization of Yersinia pseudotuberculosis harboring the pYV
M Simonet1, S Richard, P Berche
1Laboratoire de Microbiologie, Hôpital Necker-Enfants Malades, Paris, France.
Abstract:
Electron microscopic evidence is presented that bacteria harboring the virulence plasmid pYV from Yersinia pseudotuberculosis are localized in extracellular sites during the course of infection in mice, often unambiguously undergoing active replication. Virulent pYV+ bacteria, often seen adherent to platelets, severely restricted granuloma formation, creating necrotic microabscesses poorly populated with inflammatory cells. This contrasts with granulomas produced by pYV- bacteria, which appear to be composed mainly of polymorphonuclear and mononuclear cells. Our results therefore strongly suggest that active replication of pYV+ bacteria predominantly, if not exclusively, occurs in vivo in extracellular sites.
Insights
Virulent Yersinia pseudotuberculosis bacteria with the pYV plasmid replicate extracellularly in mice, hindering granuloma formation. This suggests active bacterial replication occurs outside host cells during infection.
Area of Science:
- Microbiology
- Pathogenesis
- Immunology
Background:
- Yersinia pseudotuberculosis is an important bacterial pathogen.
- The virulence plasmid pYV plays a critical role in Yersinia pathogenesis.
- Understanding bacterial replication sites is crucial for controlling infection.
Purpose of the Study:
- To investigate the in vivo replication sites of virulent Yersinia pseudotuberculosis harboring the pYV plasmid.
- To examine the impact of pYV+ bacteria on host inflammatory responses, specifically granuloma formation.
Main Methods:
- Electron microscopy was used to visualize bacteria within infected mouse tissues.
- Comparison of tissue pathology between infections with pYV+ and pYV- Yersinia pseudotuberculosis strains.
Main Results:
- Electron microscopy confirmed that pYV+ Yersinia pseudotuberculosis primarily localizes to extracellular sites during mouse infection.
- Active bacterial replication was observed in these extracellular locations.
- pYV+ bacteria, often associated with platelets, significantly restricted granuloma formation, leading to necrotic microabscesses with limited inflammatory cell infiltration, unlike pYV- infections.
Conclusions:
- The study strongly suggests that active replication of pYV+ Yersinia pseudotuberculosis predominantly occurs in extracellular sites in vivo.
- Extracellular replication and association with platelets may contribute to immune evasion by limiting inflammatory responses.