Based on previous studies of our group in which we demonstrated that dalbavancin loaded in bone cement had good elution capacity for the treatment of biofilm-related periprosthetic infections, we now assess the anti-biofilm activity of dalbavancin and compare it with that of vancomycin up to a 3-month period. We performed an in vitro model based on calculation of percentage reduction of log cfu/ml counts of sonicated steel discs contaminated with Staphylococci and further exposed to bone cement discs loaded with 2.5% or 5% vancomycin and dalbavancin at each study period (24 hours, 48 hours, 1 week, 2 weeks, 6 weeks, 3 months). In addition, we tested the anti-biofilm activity of eluted vancomycin and dalbavancin at each study period based on a 96-well plate model assessing percentage reduction of metabolic activity. Overall, dalbavancin showed a significant concentration decrease from 2 weeks of incubation and maintain its anti-biofilm activity up to 3 months, whereas, despite vancomycin showed a significant decrease at 1w and then it gradually increased, its anti-biofilm activity was significantly lower. Dalbavancin percentage reduction cfu/ml counts were higher than those of vancomycin, both at 2.5% and 5% concentrations. Reduction of log cfu/ml counts were higher for S. epidermidis than for S. aureus, being more notable for 5% dalbavancin at month 3. In addition, percentage reduction of metabolic activity also decreased at 3 months in 5% dalbavancin and 5% vancomycin, being more notable in the last.

Background: Number of joint infections caused by Vancomycin-resistant pathogens is emerging. Currently no PMMA cement is commercially available to cover VRE. Daptomycin shows promising results in infection treatment, offers a good safety profile and reduced risk for resistance development. Purpose of this in vitro study is to investigate the mechanical stability, handling properties, elution behavior and antimicrobial effectiveness of PMMA cement loaded with three different Daptomycin concentrations in comparison to commercially available ALBC; Methods: Mechanical properties and handling characteristics (ISO 5833, DIN 53435), HPLC elution, antimicrobial effectiveness with proliferation assay (DIN 17025) and inhibition zone testing were investigated; Results: All tested Daptomycin concentrations fulfilled ISO and DIN mechanical strength. Dosage of 0.5. g added Daptomycin did not show any antimicrobial effectiveness in contrast to 1.0 g and1.5 g. Cement with 1.5 g Daptomycin was best in elution and effectiveness, showed good mechanical ISO strength, ISO doughing was a little longer sticky and setting was faster as Vancomycin containing reference cement; Conclusion: PMMA cement containing 0.5 g Gentamicin and 1.5 g Daptomycin could be a good alternative to the already established COPAL® G+V for PJI treatment of VRE.