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Role of attachment for the virulence of Streptococcus pneumoniae
B Andersson1, B Gray, C S Edén
1Department of Clinical Immunology, University of Göteborg, Sweden.
Abstract:
Adherence of microorganisms to mucosal surfaces is a general phenomenon among microorganisms infecting the human host. Its role for persistence and colonization as well as production of local inflammation is well established. This paper describes the adhesion of Streptococcus pneumoniae to human epithelial cells. Strains from various anatomical sites or diseases are compared for attaching capacity. Isolates from the same host but at different times are also compared. The molecular mechanisms, the so-called adhesin-receptor interactions, are partially described. The pneumococcus recognizes a sugar sequence; GlcNAc beta 1-3Gal; on the surface of the host epithelial cell. Glycoconjugates containing this disaccharide act as receptors for adhering pneumococci. The adhesin in pneumococcal attachment is less well characterized. It is a heat and trypsin sensitive component, most likely a peptide, which forms a bridge between the receptor and an anchoring site in the pneumococcal cell wall. Receptor active saccharides are part of the adhesion-inhibitory activity found in human milk.
Insights
Streptococcus pneumoniae adheres to human epithelial cells by recognizing a specific sugar sequence. This interaction, involving adhesins and receptors, is crucial for bacterial colonization and inflammation.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Microorganism adherence to mucosal surfaces is key for host colonization and inflammation.
- Streptococcus pneumoniae is a significant human pathogen known to colonize mucosal surfaces.
Purpose of the Study:
- To investigate the adherence capacity of Streptococcus pneumoniae to human epithelial cells.
- To elucidate the molecular mechanisms underlying pneumococcal-epithelial cell interactions, focusing on adhesin-receptor binding.
Main Methods:
- Comparison of adherence capacity among different Streptococcus pneumoniae strains from various anatomical sites and disease states.
- Analysis of isolates from the same host over time to assess changes in attachment.
- Characterization of the molecular interactions, including identification of the specific sugar sequence recognized by pneumococci and properties of the adhesin.
Main Results:
- Streptococcus pneumoniae recognizes the sugar sequence N-acetylglucosamine beta 1-3galactose (GlcNAc beta 1-3Gal) on host epithelial cells.
- Glycoconjugates containing this disaccharide serve as receptors for pneumococcal attachment.
- The pneumococcal adhesin involved is a heat- and trypsin-sensitive component, likely a peptide, mediating binding to the epithelial cell receptor and the bacterial cell wall.
Conclusions:
- The specific recognition of GlcNAc beta 1-3Gal by Streptococcus pneumoniae is a critical factor in its adherence to human epithelial cells.
- Understanding these adhesin-receptor interactions provides insights into pneumococcal colonization and pathogenesis.
- Human milk contains saccharides that inhibit this adhesion process, suggesting a potential role in host defense.