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Journal of Bone and Joint Surgery - British Volume, Vol 84-B, Issue 5,
758-760.
doi: 10.1302/0301-620X.84B5.11907 Copyright © 2002 by British Editorial Society of Bone and Joint Surgery Development of resistant strains of Staphylococcus epidermidis on gentamicin-loaded bone cement in vivoB. Thornes, FRCS I, Orthopaedic Registrar; P. Murray, FRCS Ed (Orth), Consultant Orthopaedic Surgeon; and D. Bouchier-Hayes, FRCS, Professor of SurgeryDepartment of Surgical Research, The Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland. Correspondence should be sent to Mr B. Thornes at 25 Haddon Court, Clontarf, Dublin 3, Ireland. We have compared the rates of infection and resistance in an animal model of an orthopaedic procedure which was contaminated with a low-dose inoculum of Staphylococcus epidermidis. We randomised 44 Sprague-Dawley rats to have bone cement implanted subcutaneously containing either gentamicin or saline (control). The wound was inoculated with a dilute solution of gentamicin-sensitive Staphylococcus epidermidis. At two weeks the cement was retrieved and microbiologically tested. A lower overall rate of infection was seen in the gentamicin-loaded cement group, but there was a significantly higher rate of gentamicin-resistant infection in this group (Fishers exact test, p < 0.01). Antibiotic-impregnated cement has an optimum surface for colonisation and prolonged exposure to antibiotic allows mutational resistance to occur. Gentamicin-loaded cement may not be appropriate for revision surgery if it has been used already in previous surgery.
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