2008 Abstract : 25

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Authors: Cantey, JR, Salgado CD, Marculescu CE

Title: Staphylococcal Infections of Orthopedic Hardware: Persistence of Infecting Strains

Institution: Medical University of South Carolina, Charleston, SC

Purpose: It is hypothesized that staphylococci can survive on orthopedic hardware for long periods of time, in spite of treatment with appropriate antibiotics.

Methods: Methicillin resistant Staphylococcus aureus (MRSA) strains isolated from infected patients and from nares cultures of all patients admitted to the hospital since 2001 were catalogued and saved as part of the infection control program of the hospital. Our collection provided an opportunity to examine sequential cultures obtained over long intervals from patients with orthopedic hardware infections. The infectious diseases consult service sees the majority of patients with infected orthopedic hardware. Patients with MRSA infections were identified prospectively during consult rounds or by review of infection control records. Once identified, they were followed prospectively to see whether new MRSA infections occurred. Strains were confirmed as being the same Staphylococcal clone by pulse field gel electrophoresis (PFGE) of DNA digests. Strains typically were identical, although strains can be considered related if they differ by less than three bands.

Results: Eight patients were available for assessment. Three had spinal hardware infection, three had orthopedic hardware for fracture stabilization, and two had knee arthroplasty infections. All had an initial infection and one or more relapses due to MRSA. The time interval from the first MRSA isolate to thelast ranged from 3 months to 16 months. All were treated with multiple courses of appropriate intravenous antibiotics, primarily vancomycin, usually followed by suppressive therapy with oral sulfamethoxasole-trimethoprin or doxycycline. Strains from the initial positive culture and from cultures of relapses had the same PFGE pattern in all cases. No two patients had an infection with the same MRSA clone.

Discussion and Conclusion: Single clones of Staphylococcus aureus proved capable of long term colonization of orthopedic hardware. Relapse of symptomatic infection occurred over long intervals, in spite of multiple courses of appropriate intravenous and oral antibiotics. New treatment strategies are required to prevent or cure orthopedic hardware infections with Staphylococcus aureus.