Staphylococcal internalization into osteoblasts: a partially conserved mechanism across the genus

Area of Science:

• Microbiology
• Molecular Biology
• Evolutionary Biology

Background:

• Staphylococcus aureus is a major pathogen causing severe infections through mechanisms like host cell internalization.
• Internalization into non-professional phagocytic cells (NPPCs) aids immune evasion and antibiotic resistance, but is poorly understood in most Staphylococcus species.
• The fibronectin-binding protein (FnBP)-fibronectin-α5β1 integrin pathway is the primary internalization route for S. aureus into NPPCs.

Purpose of the Study:

• To investigate the genus-level capacity of Staphylococcus species to internalize into osteoblasts.
• To correlate osteoblast internalization with the presence of FnBP-like proteins.
• To explore the evolutionary conservation of the S. aureus internalization pathway.

Main Methods:

• Screened 53 Staphylococcus species for osteoblast internalization.
• Utilized fibronectin adhesion assays and osteoblast infection models.
• Performed in silico genome analysis to identify FnBP-like proteins.

Main Results:

• Half of the tested Staphylococcus species demonstrated significant internalization into osteoblasts.
• The FnBP-fibronectin-α5β1 integrin-dependent pathway is conserved in 27 species.
• In silico analysis revealed diverse FnBP-like proteins in highly internalized species, suggesting horizontal gene transfer.

Conclusions:

• Osteoblast internalization is a partially conserved trait within the Staphylococcus genus.
• The conserved internalization mechanism raises questions about the evolution of pathogenicity in staphylococci.
• Understanding this conserved mechanism is crucial for developing strategies against persistent Staphylococcus infections.