Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Surgery

Supervisor

Vasarhelyi, Edward M.

2nd Supervisor

Heinrichs, David E.

Co-Supervisor

Abstract

We sought to analyse the antimicrobial properties of exogenous copper in human synovial fluid against Staphylococcus aureus. We performed several in-vitro growth and viability assays to determine the capability of multiple S. aureus strains to survive in synovial fluid under different growth conditions. S. aureus UAMS-1 significantly died at 24 hours (p=0.017), and S. aureus USA300 WT survived at 24 hours. We confirmed a high sensitivity to killing with the addition of exogenous copper on both strains at 4 (p=0.011), 12 (p=0.011), and 24 hours (p=0.011). Both WT and CopAZB-deficient USA300 strains significantly died in synovial fluid, evidencing a minimum bactericidal concentration of copper of 50 µM against USA300 WT (p=0.011). Synovial fluid has antimicrobial properties against S. aureus, and the addition of 10µM of copper was highly bactericidal for both strains. Furthermore, we identified the CopAZB proteins as potential targets and the use of low exogenous copper concentrations as possible treatment alternatives against S. aureus.

Summary for Lay Audience

Staphylococcus aureus is the most frequently isolated organism in periprosthetic joint infections. The mechanism by which the synovial fluid kills bacteria has not yet been elucidated. We sought to analyse the antimicrobial properties of exogenous copper in human synovial fluid against S. aureus. Synovial fluid samples were collected from patients undergoing total joint arthroplasty. Different S. aureus strains were used. We first performed in-vitro growth assays with the different S. aureus strains in human synovial fluid. Viability assays were then performed to determine the capability to survive in synovial fluid with the addition of exogenous cooper. After confirming the antimicrobial effect of copper against S. aureus, we compared the differences in sensitivity between a highly resistant and mutant deficient strain. The sensitive strain significantly died after 24 hours, whereas the resistant strain survived after 24 hours. Both strains significantly died after 4, 12, and 24 hours with the addition of exogenous copper, confirming its role as an antimicrobial agent against S. aureus. Finally, the protein deficient strain was susceptible to lower copper concentrations. In light of these findings, we confirmed the antimicrobial properties of synovial fluid and the bactericidal effect of exogenous copper against S. aureus. Although future and well-designed studies might be needed, we propose using exogenous copper and target bacterial proteins as possible treatment alternatives against S. aureus infections.

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