Development of resistant strains of Staphylococcus epidermidis on gentamicin-loaded bone cement in vivo.
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 (Fisher's 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.
Thomes
B
B
Department of Surgical Research, The Royal College of Surgeons, Beaumont Hospital, Dublin, Ireland.
Murray
P
P
Bouchier-Hayes
D
D
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001843:Bone Cements; D004337:Drug Carriers; D004352:Drug Resistance, Microbial; D005839:Gentamicins / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D023421:Models, Animal; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012086:Reoperation; D013212:Staphylococcus epidermidis / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D001843:Bone Cements; D004337:Drug Carriers; D005839:Gentamicins