Balancing strength and sterility: An in vitro assessment of the mechanical and antibacterial properties of bone cement loaded with various antibiotics.

Abstract

Objectives: This study aims to determine the antimicrobial efficacy and mechanical strength of antibiotic-loaded cement samples in which daptomycin, vancomycin, teicoplanin, meropenem and piperacillin-tazobactam agents were mixed at different doses and to investigate the differences between agents and between doses.

Materials and methods: We prepared standardized bone cement samples incorporating vancomycin, teicoplanin, daptomycin, piperacillin-tazobactam, and meropenem at concentrations ranging from 0.625 to 15%. Samples underwent six-week phosphate-buffered saline immersion simulating physiological conditions. Mechanical testing employed four-point bending analysis following ISO 5833 standards. Antimicrobial efficacy was assessed using liquid microdilution against Staphylococcus aureus and Pseudomonas aeruginosa over 21 days.

Results: All antibiotics demonstrated strong negative correlation between concentration and mechanical strength (r=-0.883 to -0.914, p<0.001). Critical threshold emerged at 5% antibiotic concentration, above which mechanical integrity was significantly compromised. Daptomycin and meropenem maintained superior mechanical properties at effective antimicrobial concentrations. At 2-g doses, daptomycin achieved significantly higher strength than piperacillin-tazobactam and teicoplanin (p=0.021). All antibiotics except low-dose piperacillin-tazobactam maintained complete antimicrobial efficacy throughout 21-day testing. Electron microscopy revealed increased porosity, which correlated with reduced mechanical strength, particularly in piperacillin-tazobactam and teicoplanin groups.

Conclusion: Antibiotic selection significantly impacts both mechanical and antimicrobial properties of bone cement. Daptomycin and meropenem offer optimal balance of antimicrobial efficacy and mechanical integrity. These findings provide evidence-based guidelines for antibiotic selection in resistant infection management while maintaining structural requirements.