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Ultrastructural study of interaction of group A streptococci with tissue culture cells
Abstract:
Submicroscopic aspects of the adherence of Group A streptococci to HEp-2 cells and the time sequence of their further interaction with these cells were studied. The M+ variant of streptococci, characterized by the presence of filamentous protrusions on the cell wall, displayed a high capacity for adherence, in contrast to the M- variant of the same strain, where adherence was low. The first stage of the interaction between M+ variant of Group A streptococci and HEp-2 cells was adherence of the filamentous protrusions of the bacterial cell wall to host cell cytoplasmic membrane; this was followed by closer contact of the streptococcus cell wall with HEp-2 cell surface. Continuing incubation led to the development of invaginations in the cytoplasmic membranes of HEp-2 cells, into which streptococci gradually penetrated. Ingestion of streptococci into the forming pseudovacuoles of the host cell was accompanied by bacterial cell division, culminating in total disintegration of the host cell and release of the streptococci into the medium. At all stages of the interaction there was a pronounced tendency to form multiple contacts between the surface structures of the streptococcus cell and the membrane structures of the animal cell being attacked.
Insights
Group A streptococci with M protein (M+) adhere strongly to host cells, unlike M- variants. M+ streptococci invade and destroy host cells through a multi-stage process involving membrane interactions and bacterial division.
Area of Science:
- Microbiology
- Cell Biology
- Pathogenesis
Background:
- Group A streptococci are significant human pathogens.
- Understanding bacterial adherence and invasion mechanisms is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the submicroscopic interactions between Group A streptococci and HEp-2 cells.
- To elucidate the time sequence of streptococcal adherence and host cell invasion.
Main Methods:
- Submicroscopic observation of Group A streptococci (M+ and M- variants) interacting with HEp-2 cells.
- Time-lapse analysis of bacterial-host cell interactions.
Main Results:
- M+ streptococci exhibited significantly higher adherence to HEp-2 cells compared to M- variants.
- The interaction involved initial adherence via filamentous protrusions, followed by HEp-2 cell membrane invagination and bacterial penetration.
- Streptococci underwent intracellular division, leading to host cell disintegration and release.
Conclusions:
- The M protein of Group A streptococci plays a critical role in adherence to host cells.
- Streptococcal invasion involves a complex sequence of events, including host cell membrane manipulation and bacterial multiplication.
- These findings provide insights into the pathogenesis of Group A streptococcal infections.