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Updated: Dec 19, 2025
Invasion of Human Cells by a Bacterial Pathogen
Published on: March 21, 2011
Characterization and pathogenicity of fibronectin binding protein FbpI of Streptococcus intermedius
Yoshitoyo Kodama1, Yu Shimoyama1, Taichi Ishikawa1
1Division of Molecular Microbiology, Department of Microbiology, Iwate Medical University, 1-1-1 Idaidori, Yahaba-cho, Shiwa-gun, Iwate, 028-3694, Japan.
Abstract:
Streptococcus intermedius is a causative agent of brain or liver abscesses. S. intermedius produces intermedilysin that plays a pivotal role in pathogenicity. We identified other pathogenic factors and described a fibronectin binding protein (FBP) homolog of S. intermedius (FbpI) that mediated bacterial adhesion to epithelial cells and virulence for mice. The amino acid sequence of FbpI is similar to that of atypical FBPs, which do not possess a conventional secretion signal and an anchoring motif. A full-length recombinant FbpI (rFbpI) bound to immobilized fibronectin in a dose-dependent manner. The fibronectin binding activity of an N-terminal construct of rFbpI comprising the translation initiation methionine of the open reading frame to lysine 265 (rFbpI-N) bound immobilized fibronectin to a much lesser extent compared with rFbpI. A construct comprising the C-terminal domain (alanine 266 to methionine 549; rFbpI-C) bound immobilized fibronectin equivalently to rFbpI. Adherence of the isogenic mutant ΔfbpI to cultured epithelial cells and immobilized fibronectin was significantly lower than that of the wild-type strain. Abscess formation of ΔfbpI reduced in a mouse infection model compared with that in the wild-type. Thus, FbpI may play a role in bacterial adhesion to host cells and represent a critical pathogenic factor of S. intermedius.
Insights
Streptococcus intermedius causes abscesses, partly due to its fibronectin binding protein (FbpI). This protein mediates bacterial adhesion and virulence, highlighting its role in pathogenicity.
Area of Science:
- Microbiology
- Pathogenesis
- Bacterial Virulence Factors
Background:
- Streptococcus intermedius is a pathogen causing brain and liver abscesses.
- Intermedilysin is a known virulence factor, but other pathogenic factors are being investigated.
- Fibronectin binding proteins (FBPs) are implicated in bacterial adhesion and pathogenicity.
Purpose of the Study:
- To identify and characterize novel pathogenic factors of Streptococcus intermedius.
- To investigate the role of a fibronectin binding protein homolog (FbpI) in bacterial adhesion and virulence.
Main Methods:
- Sequence analysis of FbpI and its comparison to atypical FBPs.
- Recombinant FbpI (rFbpI) production and fibronectin binding assays.
- Construction and analysis of an isogenic mutant (ΔfbpI) for adherence and mouse infection models.
Main Results:
- FbpI demonstrated dose-dependent binding to fibronectin, with the C-terminal domain being crucial for this interaction.
- The ΔfbpI mutant showed significantly reduced adherence to epithelial cells and fibronectin.
- Abscess formation was reduced in the ΔfbpI mutant mouse infection model compared to the wild-type.
Conclusions:
- FbpI is a novel fibronectin binding protein of Streptococcus intermedius.
- FbpI plays a significant role in bacterial adhesion to host cells and contributes to virulence.
- FbpI represents a critical pathogenic factor for S. intermedius infections.
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