Antimicrobial properties and elution kinetics of linezolid from polymethylmethacrylate

Polymethylmethacrylate (PMMA) impregnated with antibiotics is widely used in the treatment of osteomyelitis and infected arthroplasties. With the emergence of resistant bacterial strains, linezolid, which is active against gram-positive bacteria and toward which resistance has been scarce, has been suggested as an alternative. In the current in vitro study, the authors sought to determine and compare the efficacy and elution kinetics of linezolid from PMMA. Polymethylmethacrylate beads impregnated with linezolid, vancomycin, or gentamicin alone and in combinations were placed in suspensions of vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, and Staphylococcus epidermidis. The leaching out concentrations of antibiotics and growth inhibitory time in days were recorded. The mechanical strength of cement beads was evaluated in accordance with International Standard 5833. The growth inhibitory time of linezolid was significantly longer than that of vancomycin and gentamicin for methicillin-resistant S aureus, vancomycin-resistant enterococci, and S epidermidis. The combination of linezolid with gentamicin and vancomycin significantly increased the growth inhibitory time compared with either antibiotic used alone. Linezolid alone or in combination with vancomycin and gentamicin showed satisfactory elution kinetics and antimicrobial activity in vitro without compromising the mechanical strength of PMMA. Future research evaluating the in vivo profile of linezolid-loaded PMMA in experimental animals is needed before it can be considered for human use.