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M protein-associated adherence of Streptococcus pyogenes to epithelial surfaces: prerequisite for virulence
Abstract:
Virulent strains of Streptococcus pyogenes containing M protein were found to adhere well to human cheek epithelial cells in vitro, whereas an avirulent M - mutant strain adhered feebly. Pretreatment of M + strains with trypsin to remove their M protein surface coating or reacting them with type-specific antiserum markedly impaired their abilities to attach to epithelial cells. Electron microscopy revealed that the attachment of an M + strain to germfree rat epithelial cells was mediated by a fuzzy surface structure previously shown to contain M protein. When mixtures of streptomycin-resistant M + and M - strains were introduced into the mouths of mice, the proportions of the M + strain increased on tongue and cheek surfaces relative to its M - mutant. These data indicate that the surface fuzz of S. pyogenes which contains M protein functions in the attachment of the organism to epithelial surfaces, thereby permitting its colonization.
Insights
Streptococcus pyogenes uses its M protein surface fuzz to attach to human epithelial cells. This attachment is crucial for bacterial colonization, as demonstrated in both in vitro and in vivo models.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Cell Adhesion
Background:
- Streptococcus pyogenes is a significant human pathogen.
- The M protein of S. pyogenes is a key virulence factor.
- Mechanisms of bacterial adherence to host cells are critical for colonization.
Purpose of the Study:
- To investigate the role of M protein in the adherence of Streptococcus pyogenes to epithelial cells.
- To elucidate the function of the M protein surface structure in bacterial colonization.
Main Methods:
- In vitro adherence assays using human cheek epithelial cells.
- Enzyme treatment (trypsin) and antiserum blocking experiments.
- Electron microscopy of bacterial attachment to rat epithelial cells.
- In vivo competition assays in mouse oral cavities.
Main Results:
- Virulent M protein-positive (M+) S. pyogenes strains adhered strongly to epithelial cells, while avirulent M protein-negative (M-) strains adhered poorly.
- Removal of M protein or blocking with antiserum significantly reduced bacterial adherence.
- Electron microscopy confirmed M protein-containing surface structures mediate attachment.
- In mice, M+ strains outcompeted M- strains on oral surfaces, indicating enhanced colonization.
Conclusions:
- The M protein surface fuzz of Streptococcus pyogenes is essential for its attachment to epithelial cells.
- This adherence mechanism facilitates bacterial colonization of host tissues.
- M protein plays a critical role in the pathogenesis of S. pyogenes infections.