Reduction in Pseudomonas aeruginosa and Staphylococcus aureus biofilms from implant materials in a diffusion dominated environment

Antibiotic‐loaded calcium sulfate beads (CS‐B) are used to treat biofilm‐related periprosthetic joint infections (PJI). A previous study has shown that such beads are effective in reducing lawns biofilms grown on agar plates; however, the ability of CS‐B to eradicate biofilms grown on solid orthopedic material surfaces has not been investigated. We grew biofilms of bioluminescent strains of Pseudomonas aeruginosa Xen41 and a USA300 MRSA Staphylococcus aureus SAP231 on ultra‐high molecular weight polyethylene (PE), hydroxyapatite (HA), and 316L stainless steel (SS) coupons for three days under static growth conditions, with daily nutrient exchange. The coupons were rinsed with sterile phosphate buffered saline (PBS) to remove planktonic bacteria and placed in a petri dish, surrounded by four either antibiotic vancomycin and tobramycin loaded (CS‐B_V+T) or unloaded beads (CS‐B_U). A thin layer of agar was overlaid to simulate a periprosthetic infection where an implant abuts soft tissue and then incubated for 72 h. The amount of biofilm was measured by bioluminescence imaging (BLI) for activity and viable cell count (CFUs). Coupons exposed to CS‐B_V+T showed a significant reduction in the amount of biofilm within 24 h, regardless of the bacterial strain or material type. The coupons exposed to control CS‐B_U had no effect on bacteria over 72 h. Statement of Clinical Significance: Antibiotic‐loaded calcium sulfate beads (CS‐B) were effective in significantly reducing mature biofilms of P. aeruginosa and S. aureus from orthopedic relevant surfaces in our in vitro agar model. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3081–3085, 2018.