Host defense proteins derived from human saliva bind to Staphylococcus aureus

Area of Science:

• Microbiology
• Oral Biology
• Pathogen-Host Interactions

Background:

• Salivary proteins are crucial for modulating oral bacterial colonization.
• Systemic pathogens like Staphylococcus aureus can colonize the oral cavity, posing risks, especially to hospitalized patients.
• Understanding salivary protein interactions with S. aureus is key to elucidating oral colonization mechanisms.

Purpose of the Study:

• To investigate the binding of salivary proteins to Staphylococcus aureus.
• To identify specific salivary components that bind to S. aureus.
• To explore the bacterial surface components involved in these interactions.

Main Methods:

• Fluorescently labeled saliva was used to study protein binding to S. aureus.
• Proteomic techniques were employed to identify bound salivary proteins.
• Staphylococcal protein A (SpA) was investigated as a potential adhesive component.

Main Results:

• S. aureus selectively binds major salivary components including DMBT1(gp-340), mucin-7, secretory component, immunoglobulins A and G, S100-A9, and lysozyme C.
• Biofilm-grown S. aureus exhibits reduced binding of salivary components, especially immunoglobulins, compared to planktonic forms.
• Staphylococcal protein A (SpA) mediates immunoglobulin binding, but other bacterial surface components are involved in binding non-immunoglobulin proteins like mucin-7.

Conclusions:

• A limited set of salivary proteins, many involved in host defense, selectively bind to S. aureus.
• Saliva may play a significant role in the oral colonization of S. aureus in the human mouth.
• Further research is needed to identify additional bacterial adhesins involved in salivary protein binding.