Staphylococcus epidermidis polysaccharide intercellular adhesin activates complement

Area of Science:

• Microbiology
• Immunology
• Infectious Diseases

Background:

• Staphylococcus epidermidis is a major cause of hospital-acquired infections.
• Biofilm formation, mediated by polysaccharide intercellular adhesin (PIA), is a key virulence factor.
• PIA and biofilms are linked to immune evasion strategies.

Purpose of the Study:

• To investigate the impact of S. epidermidis PIA on the host inflammatory response.
• To specifically examine the role of PIA in complement activation.
• To compare the immune-modulating effects of PIA-positive and PIA-negative S. epidermidis strains.

Main Methods:

• Utilized a human whole-blood ex vivo infection model.
• Compared a PIA-positive strain (SE1457) with its PIA-negative isogenic mutant (M10).
• Investigated the independent effect of purified PIA on complement activation.

Main Results:

• SE1457 formed a PIA-rich biofilm, while the mutant formed a proteinaceous, DNA-rich biofilm.
• PIA-positive strain induced stronger complement system activation compared to the mutant.
• Purified PIA independently triggered significant complement activation.
• The PIA-negative mutant induced greater granulocyte activation (CD11b) and cytokine secretion.

Conclusions:

• S. epidermidis PIA possesses potent pro-inflammatory properties via complement activation.
• The reduced granulocyte and cytokine activation by PIA biofilms may impede bacterial clearance.
• A complex interplay exists between PIA-mediated complement activation and other immune responses in S. epidermidis infections.