Reduction in Pseudomonas aeruginosa and Staphylococcus aureus biofilms from implant materials in a diffusion dominated environment: Diffusion mediated biofilm eradication

Abstract

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 orthopaedic material surfaces has not been investigated. We grew biofilms of bioluminescent strains of Pseudomonas aeruginosa Xen41 and a USA300 MRSA Staphylococcus aureus SAP231 on an 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-BV+T) or unloaded beads (CS-BU). A thin layer of agar was overlaid to simulate a periprosthetic infection where an implant abuts soft tissue, then incubated for 72 hours. The amount of biofilm was measured by bioluminescence imaging (BLI) for activity and viable cell count (CFUs). Coupons exposed to CS-BV+T showed a significant reduction in the amount of biofilm within 24 hours, regardless of the bacterial strain or material type. Whereas, coupons exposed to control CS-BU had no effect on bacteria over 72 hours. 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 orthopaedic relevant surfaces in our novel in vitro periprosthetic-soft tissue model.

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ORCID for Paul Stoodley: orcid.org/0000-0001-6069-273X

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