In vitro adherence and accumulation of Staphylococcus epidermidis RP 62 A and Staphylococcus epidermidis M7 on four different bone cements

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Abstract
Bacterial resistance of Staphylococcus epidermidis, a serious pathogen of implant-related infections, to antibiotics is related to the production of a glycocalyx slime that impairs antibiotic access and the killing by host defense mechanisms. In vitro studies of different bone cements containing antibiotics, developed for the prevention of biomaterial-associated infection, could not always demonstrate complete eradication of biomaterial-adherent bacteria. We have investigated four different bone cements in regard to bacterial accumulation of a slime-producing strain RP 62 A and its isogenic mutant M7 lacking the ability to produce exopolysaccharide slime using a bacterial adhesion assay and modified Kirby-Bauer technique. A significant effect of exopolysaccharide production for the accumulation on bone cement could be demonstrated. The gentamicin/clindamycin bone cement was the only tested biomaterial that produced a large zone of bacterial inhibition in the inoculated area adjacent to the biomaterial. The bacterial adhesion was not reduced significantly and there was no correlation between zones of inhibition on blood agar plates and the quantitative adhesion assay. The clinical efficacy of the gentamicin/clindamycin bone cement must be proven in vivo.