Immunotherapy synergizes with debridement and antibiotic therapy in a murine 1‐stage exchange model of MRSA implant‐associated osteomyelitis

ABSTRACT Methicillin‐resistant Staphylococcus aureus (MRSA) reinfection following revision surgery remains a major orthopaedic problem. Toward the development of immunotherapy with anti‐glucosaminidase monoclonal antibodies (anti‐Gmd), we aimed to: (i) develop a murine 1‐stage exchange model of bioluminescent MRSA (USA300LAC::lux) contaminated femoral implants; and (ii) utilize this model to demonstrate the synergistic effects of combination vancomycin and anti‐Gmd therapy on reinfection and bone healing. Following an infection surgery, the original plate and two screws were removed on day 7, and exchanged with sterile implants. Mice were randomized to five groups: (i) no infection control; (ii) infected placebo; (iii) anti‐Gmd; (iv) vancomycin; and (v) combination therapy. Bioluminescent imaging (BLI) was performed on days 0, 1, 3, 5, 7, 8, 10, 12, and 14. Mice were euthanized on day 14 (day 7 post‐revision), and efficacy was assessed via colony forming units (CFU) on explanted hardware, micro‐CT, and histology. As monotherapies, anti‐Gmd inhibited Staphylococcus abscess communities, and vancomycin reduced CFU on the implants. However, only combination therapy prevented increased BLI post‐revision surgery, with a significant 6.5‐fold reduction on day 10 (p