Implant-Associated Localized Osteitis in Murine Femur Fracture by Biofilm Forming Staphylococcus aureus: A Novel Experimental Model

Staphylococcus aureus (SA) is the most common causative agent for implant-associated osteitis. The present study characterizes a novel model of a low grade acute SA osteitis with bone defect in the femur which is stabilized by a titanium locking plate. Wild-type Balb/c mice were osteotomized, fixed by a locking plate and infected with SA. Mice underwent debridement 7 and 14 days later and were sacrificed at Day 28. At Days 7, 14, and 28 after inoculation local and systemic cell populations and IL-6 were analyzed. Fracture healing was quantified by radiography. The control group underwent the same procedure without infection. The bacterial load of implant-associated osteitis with biofilm formation was quantified by counting CFU and real-time PCR. Fracture healing determined by radiography was delayed in infected compared to non-infected mice. Throughout the investigation period CFU and leukocyte counts, as well as IL-6 levels were found to be significantly elevated in infected mice at the infection site but not systemically. Our murine model allows the detailed investigation of implant associated localized osteitis with biofilm producing SA and its influence on fracture healing. The model provides a tool to analyze therapeutic or prophylactic approaches to the problem of biofilm-associated osteitis. (c) 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:2013-2020, 2013