BACKGROUND: The increasing incidence of bacterial infections in orthopedic surgery might be related to the increasing application of artificial devices. In most cases, bacteria multiply on the surface of implants in biofilms. Poor penetration of antibiotics, frequent necessity of prosthesis removal, chronic processes and financial costs emphasize the significance of preventive measures. METHOD: Adhesion of bacterial strains (two Staphylococcus aureus, two coagulase-negative staphylococci and two Pseudomonas aeruginosa strains isolated from orthopedic patients' wounds) to the surface of a polyethylene cup was investigated using an ultrasonic method. Results were compared to the adhesive ability of three Hungarian standard strains. The effect of antibiotic treatment (cefuroxime, cefotaxime, amoxicillin with clavulanic acid and amikacin) has been examined. RESULTS: The staphylococcal strains showed significantly higher adhesive ability than Pseudomonas strains. Antibiotic treatment significantly reduced the attachment of bacteria. The higher the concentration of the antibiotics, the higher was the decrease in bacterial adhesion. CONCLUSIONS: Antibiotic prophylaxis was proven to be effective against bacterial adhesion, and, if applied at the proper time at the highest tolerable dose, it might prevent the formation of biofilms. Copyright 2005 S. Karger AG, Basel.