Gentamicin release from polymethylmethacrylate bone cements and Staphylococcus aureus biofilm formation

We measured the formation of a Staphylococcus aureus biofilm in vitro on un loaded and gentamicin-loaded bone cements (CMW3 and Palaces R) and related the formation to antibiotic release rates. All experiments were done in tri plicate. Microbial growth on gentamicin-loaded cements occurred despite the release of antibiotic. Biofilm formation an gentamicin loaded CMW3 bone ce ment was one fourth to one fifth less than on the unloaded bone cement, whi le biofilm formation an Palacos R bone cement was not significantly affecte d by antibiotic loading. More gentamicin was released from CMW3 (79 mg) tha n from Palacos R (70 mg), but the percentage gentamicin released after one week relative to the total amount incorporated was significantly lower for CMW3 (4.7%) than for Palaces R (8.4%), After one day, subinhibitory concent rations of antibiotics were eluted from the cements. We concluded that anti biotic-loaded bone cement does not necessarily inhibit the formation of an infectious biofilm in vitro.