NOVEL ANIMAL-MODEL FOR STUDYING THE MOLECULAR MECHANISMS OF BACTERIALADHESION TO BONE-IMPLANTED METALLIC DEVICES - ROLE OF FIBRONECTIN IN STAPHYLOCOCCUS-AUREUS ADHESION

Infection around metallic implants is a rare but severe complication o f orthopaedic surgery. A novel animal model mimicking conditions of in ternal fixation devices was developed to evaluate the role of host pro teins adsorbed on metallic devices in promoting adhesion and colonizat ion of the material surfaces by Staphylococcus aureus. Small plates ma de of pure titanium were either fixed (three screws per plate) onto th e iliac bones of guinea pigs or implanted into their subcutaneous spac e as controls. Five to 6 weeks after surgery, the plates and screws we re removed from the previously killed animals, carefully rinsed in buf fer, and tested in an in vitro assay of S. aureus adhesion to metallic surfaces. To evaluate the role of fibronectin in staphylococcal adhes ion to explanted plates and screws, a mutant of S. aureus that is spec ifically defective in fibronectin adhesion due to decreased expression of the fibronectin adhesin was compared with its isogenic parental st rain. A significant reduction in adhesion of the fibronectin adhesin-d efective mutant compared with the parental strain occurred on both the subcutaneously implanted and bone-implanted metallic plates. The resu lts of this specific biological assay suggest that fibronectin is pres ent on bone-implanted metallic devices and promotes attachment of S. a ureus to their surfaces. This novel experimental model should help to characterize several parameters of bacterial adhesion to metallic orth opaedic devices and to develop novel anti-adhesive strategies for prev enting such infections.