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Plasmid-mediated contact haemolytic activity in Shigella species: correlation with penetration into HeLa cells
P Clerc1, B Baudry, P J Sansonetti
1Service des Entérobactéries, Unité INSERM 199, Institut Pasteur, Paris.
Abstract:
The main feature of virulent strains of Shigella is their ability to invade eucaryotic cells. This phenotype is both plasmid-mediated and temperature-regulated. In the present report, we demonstrate a plasmid-mediated and temperature-regulated haemolytic activity in S. flexneri, S. dysenteriae and S. sonnei. Detection of this haemolytic activity requires centrifugation of suspensions containing bacteria and erythrocytes, followed by incubation of the pellets at 37 degrees C. No soluble intra- or extracellular haemolytic activity could be detected. Dose-effect and electron microscopic studies demonstrated that direct contact of several virulent bacteria per erythrocyte was critical for haemolysis to occur. However, no local morphological alteration of the erythrocyte membrane at the site of contact with bacteria could be detected. Intensity of this haemolytic activity was fully correlated with the efficiency of penetration within HeLa cells, suggesting a common mechanism for induction of phagocytosis and lysis of erythrocytes.
Insights
Virulent Shigella strains exhibit temperature-regulated, plasmid-mediated hemolytic activity. This activity requires direct bacterial contact with erythrocytes and correlates with cell invasion efficiency, suggesting a shared mechanism.
Area of Science:
- Microbiology
- Cell Biology
- Pathogenesis
Background:
- Virulent Shigella strains possess the ability to invade eukaryotic cells.
- This invasion is a plasmid-mediated and temperature-regulated phenotype.
- Understanding Shigella virulence factors is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the presence and characteristics of hemolytic activity in virulent Shigella strains.
- To determine the relationship between hemolytic activity and bacterial invasion of host cells.
- To elucidate the mechanism underlying Shigella-induced hemolysis.
Main Methods:
- Culturing of Shigella flexneri, S. dysenteriae, and S. sonnei strains.
- Assaying hemolytic activity through centrifugation and incubation of bacteria with erythrocytes at 37°C.
- Utilizing dose-effect studies and electron microscopy to analyze bacterial-erythrocyte interactions.
- Quantifying bacterial invasion efficiency in HeLa cells.
Main Results:
- Demonstrated plasmid-mediated and temperature-regulated hemolytic activity in S. flexneri, S. dysenteriae, and S. sonnei.
- Hemolysis required direct bacterial contact with erythrocytes; no soluble activity was detected.
- Hemolytic activity intensity strongly correlated with the efficiency of bacterial penetration into HeLa cells.
Conclusions:
- Shigella-induced hemolysis is dependent on direct bacterial contact and is linked to the invasion mechanism.
- The findings suggest a common pathway for erythrocyte lysis and host cell phagocytosis.
- This hemolytic activity serves as a potential indicator of Shigella virulence.