Domain antibody–displayed phages as a novel biofilm-targeted therapy for Staphylococcus aureus
摘要
Chronic hyperglycemia in diabetic patients promotes Staphylococcus aureus colonization and biofilm formation, contributing to persistent infection and poor wound healing in diabetic foot ulcers (DFUs). Biofilms hinder antibiotic penetration and promote resistance, highlighting the need for targeted anti-biofilm strategies. In this study, domain antibody–displaying M13 phages were developed to selectively target S. aureus biofilms. Among the selected clones, A7-displayed phage showed the strongest binding to S. aureus based on indirect ELISA and exhibited potent, dose-dependent inhibition of biofilm formation without affecting bacterial viability. This non-bactericidal, anti-virulence effect was associated with a significant reduction in staphyloxanthin production, a pigment linked to oxidative stress resistance. Quantitative RT-PCR analysis further revealed that A7 and C1 downregulated the expression of icaA, a key gene involved in biofilm matrix synthesis. Despite its efficacy, checkerboard synergy testing showed that combining A7-displayed phage with ampicillin resulted in an antagonistic interaction (FICI > 4), suggesting that A7 is most effective as a standalone anti-biofilm agent. Target identification using far-western blotting and MS/MS analysis revealed that A7 binds specifically to a cadmium-transporting ATPase, and molecular docking analysis showed A7 interaction with the C-terminal helical domain of CadA, potentially affecting cadmium efflux and oxidative stress homeostasis. This disruption may underlie the observed biofilm inhibition. These findings establish A7-displayed phage as a promising, non-cytotoxic biotherapeutic targeting S. aureus biofilms, offering a novel strategy for DFU management and other chronic infections where conventional antibiotics fall short.