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Efficacy of antibiotics alone for orthopaedic device related infections
Z U Isiklar1, R O Darouiche, G C Landon
1Department of Orthopedic Surgery, Baylor College of Medicine, Houston, TX, USA.
Abstract:
Treatment of orthopaedic device related infections with antibiotics alone generally has been thought to be inadequate. A rabbit model was used to compare the efficacy of 4 different antibiotic regimens for treating orthopaedic device related infection caused by slime producing Staphylococcus epidermidis. After bacterial inoculation of a hole drilled through the intercondylar notch, a stainless steel screw was placed into the femur. Two weeks later, rabbits were randomized to receive a 2-week course of antibiotics: (1) 9 rabbits received vancomycin alone; (2) 10 rabbits received minocycline alone; (3) 10 rabbits received vancomycin plus rifampin; and (4) 10 rabbits received minocycline plus rifampin. Quantitative bone cultures were performed, and antibiotic levels in serum, bone, and biofilm were determined. Despite high levels of vancomycin in biofilm, infection was never cured by vancomycin alone and was eradicated in only 20% of rabbits that received minocycline alone. The highest cure rate (90%) was achieved with the combination of vancomycin and rifampin, whereas the combination of minocycline and rifampin yielded a cure rate of 70%. These results encourage the clinical evaluation of the combination of vancomycin and rifampin in patients in whom infected orthopaedic device cannot be removed.
Insights
Antibiotic treatment for orthopaedic device infections is often inadequate. Combining vancomycin with rifampin achieved a 90% cure rate in a rabbit model, suggesting clinical potential for infected devices.
Area of Science:
- Orthopaedic Surgery
- Infectious Diseases
- Pharmacology
Background:
- Orthopaedic device-related infections pose significant treatment challenges.
- Antibiotics alone are generally considered insufficient for eradicating these infections.
Purpose of the Study:
- To compare the efficacy of four antibiotic regimens in a rabbit model for treating Staphylococcus epidermidis orthopaedic device-related infections.
- To evaluate antibiotic levels in bone and biofilm.
Main Methods:
- A rabbit model with a stainless steel screw in the femur was infected with Staphylococcus epidermidis.
- Rabbits received 2-week courses of vancomycin alone, minocycline alone, vancomycin plus rifampin, or minocycline plus rifampin.
- Quantitative bone cultures and antibiotic level determinations were performed.
Main Results:
- Vancomycin alone did not cure infections, despite high biofilm levels.
- Minocycline alone achieved a 20% cure rate.
- Vancomycin plus rifampin yielded the highest cure rate (90%).
- Minocycline plus rifampin resulted in a 70% cure rate.
Conclusions:
- The combination of vancomycin and rifampin demonstrated superior efficacy in eradicating orthopaedic device-related infections in this model.
- These findings support clinical investigation of vancomycin and rifampin for treating infected, non-removable orthopaedic devices.