Effect of gentamicin loaded PMMA bone cement on Staphylococcus aureus biofilm formation

Abstract

PMMA (poly‐methyl‐methacrylate) bone cement is widely used in prosthetic implant surgery and is currently prepared with vacuum‐mixing for improved mechanical properties. Revision of implants due to infection occurs in about 1% of cases, mostly involving staphylococcal strains. Antibiotic loaded cement is often used in this revision‐setting. The aims of this study were to determine in a modified Robbins device whether gentamicin loaded PMMA bone cements (2.5 weight percent, CMW; 1.25 weight percent, Palacos) inhibit Staphylococcus aureus ATCC 12600 biofilm formation, and whether vacuum‐mixing or hand‐mixing of the antibiotic loaded cements have an effect on biofilm inhibition. The results show that CMW antibiotic loaded bone cement reduced biofilm formation by 42 and 63% compared with the unloaded cement for vacuum‐ and hand‐mixed, respectively. Palacos, however, despite possessing half the concentration of gentamicin, demonstrated a biofilm reduction of 16 and 43% compared with the unloaded cement for vacuum‐ and hand‐mixed, respectively. High vacuum mixing of the CMW antibiotic loaded bone cement resulted in an apparent increase in biofilm formation. It is concluded that the antibiotic content of gentamicin loaded bone cements can be reduced to lower doses than effective for reducing biofilm formation by increasing the vacuum applied during preparation. In addition, increased antibiotic concentrations in a cement are not necessarily accompanied by a greater reduction in biofilm formation.