Staphylococcus aureus biofilm formation on different gentamicin-loaded polymethylmethacrylate bone cements

In this in vitro study, the formation of a Staphylococcus aureus biofilm on six gentamicin-loaded bone cements (CMW1, CMW3, CMW Endurance, CMW2000, Pa lacos. and Palamed) was determined in a modified Robbins device over a 3 da ys time span and related with previously (Van de Belt et al., Biomaterials 21 (2000) 1981) measured kinetics of antibiotic release by these cement bra nds. The influence of gentamicin release on biofilm formation was quantifie d by expressing the number of colony-forming units on gentamicin-loaded cem ent relative to the number of viable organisms on unloaded cement of the sa me brand. Biofilms formed on all gentamicin-loaded cements, despite the rel ease of antibiotics. followed a consistent pattern in time with a maximum n umber of colony-forming units per unit cement area found between 24 and 30 h after inoculation. None of the gentamicin-loaded cements showed a reducti on in biofilm formation relative to unloaded cements within 6 h after inocu lation, whereas only gentamicin-loaded CMW1 and Palacos reduced biofilm for mation 24 h after inoculation. Alternatively, CMW Endurance. CMW2000, and P alamed did not exhibit any initial reductions in biofilm formation, but eff ects started after 72, 48, and 72 h. respectively. Biofilm reduction by gen tamicin-loaded CMW3 lasted the longest from 24 to 72 h. Interestingly, each cement seemed to have a different "window-of-effectiveness" with regard to reduction in biofilm formation that did not relate with the gentamicin-rel ease kinetics. Summarising, this study demonstrates that although gentamici n loading of bone cements yields reductions in biofilm formation, S. aureus is able to grow on gentamicin-loaded bone cements. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.