Systemic antibiotic therapy does not significantly improve outcome in a rat model of implant-associated osteomyelitis induced by Methicillin susceptible Staphylococcus aureus

Treatment of implant-associated osteomyelitis regularly involves the use of systemic antibiotics in addition to surgical intervention. However, it remains unclear if perioperative systemic application of bactericide substances can improve overall outcome in models of severe intramedullary infection. The present study investigated the use of systemic gentamicin in addition to a controlled local release from a highly lipophilic gentamicinpalmitate compound while the previous study showed efficacy of sole antibiotic implant-coating. Forty male Sprague-Dawley rats were divided into two groups receiving an intramedullary femoral injection of 10(2) CFU of a common methicillin susceptible Staphylococcus aureus strain (MSSA Rosenbach). Group I received an uncoated implant whereas group II received a coated implant. All animals received a single shot intraperitoneal application of gentamicinsulfate directly after wound closure while the historical control group III (n = 20) had no antibiotic treatment at all. Animals were observed for 28 and 42 days. Serum haptoglobin and relative weight gain were assessed as well as roll over cultures of explanted femur nails and histological scores of periprosthetic infection in dissected femora. Systemic application of gentamicin combined with antibiotic-coated implant did not further reduce bacterial growth significantly compared with systemic or local antibiotic application alone. Combined local and systemic therapy reduced serum haptoglobin significantly after day 7, 28 and 42 whereas systemic application alone did not compare to controls. Systemic perioperative and implant-associated application of antibiotics were both comparably effective to treat implant-associated infections whereas the combined antibiotic therapy further reduced systemic signs of infection time dependent.