Related Experiment Videos
Electron microscopy of group A streptococci after phagocytosis by human monocytes
Abstract:
Group A streptococci were added to cultures of isolated human blood monocytes. The bacteria were readily sequestered within phagocytic vacuoles after being coated with flocculent material, apparently derived from the plasma-containing medium. Progressive lysis of intravacuolar streptococci was observed, characterized by plasmolysis, internal disruption, and eventual plasma membrane dissolution. However, the cell walls remained essentially identical to those of nonphagocytized streptococci, showing no signs of dissolution within the limited in vitro survival time of the monocytes. These results indicate that streptococcal cell walls may persist in migrating human phagocytes in vivo and may be deposited in body tissues. This cell wall material, known to be toxic to animal tissues, may be an important determinant in the pathogenesis of poststreptococcal sequelae in man.
Insights
Group A streptococci lysis occurs within human monocytes, but their toxic cell walls persist. This persistence may contribute to the pathogenesis of post-streptococcal diseases.
Area of Science:
- Immunology
- Microbiology
- Pathogenesis
Background:
- Group A streptococci (GAS) are significant human pathogens.
- Understanding GAS-host interactions is crucial for disease pathogenesis.
- Monocytes play a key role in innate immune response to bacterial infections.
Purpose of the Study:
- To investigate the fate of Group A streptococci within human blood monocytes.
- To determine if streptococcal cell walls are degraded during phagocytosis.
- To explore the potential role of persistent cell wall components in disease.
Main Methods:
- In vitro culture of isolated human blood monocytes.
- Exposure of monocytes to Group A streptococci.
- Microscopic observation of bacterial lysis and cell wall integrity within phagocytic vacuoles.
Main Results:
- Group A streptococci were rapidly phagocytosed by monocytes.
- Intravacuolar bacteria underwent lysis, with plasma membrane dissolution.
- Streptococcal cell walls remained intact, showing no degradation within the observed timeframe.
- Intact cell walls persisted within monocytes after bacterial lysis.
Conclusions:
- Human monocyte phagocytosis leads to streptococcal lysis but not cell wall degradation.
- Persisting streptococcal cell walls in phagocytes may be deposited in tissues.
- Toxic streptococcal cell wall components may contribute to post-streptococcal sequelae pathogenesis.