Universal antibacterial activity of silver against clinical MRSA isolates: relationship between biofilm characteristics and antimicrobial efficacy

Background: This study investigated the major biofilm components of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from periprosthetic joint infections (PJI) and evaluated the antibacterial activity of Kyocera’s silver-containing hydroxyapatite (Ag-HA) discs against strains with distinct biofilm characteristics. Methods: The MRSA strains examined were USA300, two PJI isolates (No.47 and No.87), and one catheter-related bloodstream infection isolate (MR10). Biofilm composition was assessed using enzymatic degradation with proteinase, DNase, or a polysaccharide-degrading enzyme, followed by quantification of the remaining biomass. The antibacterial effects of Ag-HA discs and their influence on biofilm architecture were analyzed using fluorescence imaging and confocal laser scanning microscopy after ICBiofilm clearing. Results: Strain No.47 produced a biofilm primarily composed of proteins and extracellular DNA, while USA300 and No.87 formed protein-dominant matrices. MR10 exhibited a polysaccharide-rich biofilm. Ag-HA discs suppressed bacterial attachment in all strains and altered their three-dimensional biofilm structures. The application of Ag-HA resulted in a rougher biofilm architecture and reduced surface coverage across all strains. Conclusions: MRSA biofilm composition varies widely among clinical isolates. Ag-HA demonstrates broad antibacterial activity and modifies biofilm architecture, indicating a potential contribution to its antimicrobial efficacy.