Survival of Staphylococcus epidermidis in Fibroblasts and Osteoblasts

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Staphylococcus epidermidis is a primary cause of medical device-related infections, particularly prosthetic joint infections.
• Biofilm formation is the widely accepted mechanism for chronic S. epidermidis infections.
• The role of immune evasion in S. epidermidis pathogenesis remains less understood.

Purpose of the Study:

• To investigate the hypothesis that S. epidermidis evades immune killing to contribute to pathogenesis.
• To explore the intracellular survival mechanisms of S. epidermidis in host cells relevant to prosthetic joint infections.
• To identify potential reservoirs for chronic or delayed S. epidermidis infections.

Main Methods:

• In vitro infection models using human fibroblasts and osteoblasts (human and mouse).
• Intracellular survival assays and characterization of bacterial location within host cells.
• Analysis of bacterial variants (small-colony variants) selected during intracellular persistence.
• Assessment of bacterial escape from host cells and subsequent biofilm formation.

Main Results:

• Prosthetic joint-associated S. epidermidis isolates demonstrated intracellular persistence within human fibroblasts and osteoblasts.
• Intracellular bacteria were primarily found within acidic phagolysosomes.
• Small-colony variants of S. epidermidis were selected during intracellular survival.
• Escaped bacteria from dead host cells initiated delayed biofilm formation on implant surfaces.

Conclusions:

• Acidic phagolysosomes within fibroblasts and osteoblasts act as critical reservoirs for S. epidermidis.
• Intracellular persistence and subsequent host cell escape contribute to the chronicity and delayed onset of S. epidermidis prosthetic joint infections.
• Immune evasion through intracellular survival is a significant pathogenic mechanism for S. epidermidis.