ULTRASOUND DECREASES THE VIABILITY OF BACTERIA ON ANTIBIOTIC-LOADED BONE CEMENTS: AN IN VITRO STUDY WITH CLINICAL STRAINS

Addition of antibiotics to the bone cement decreases the incidence of infection. However, the antibiotic is only partially released. Ultrasound may increase the antibiotic release and furthermore the effectiveness of the antibiotic might be enhanced by the so-called bio-acoustic effect. The objective of this study was twofold. The first aim was to evaluate to what extent antibiotic release from bone cement could be increased by ultrasound. The second aim was to investigate the viability of bacteria when antibiotic release from bone cements was combined with ultrasound. Cylindrical bone cement samples of Palacos R-G (loaded with gentamicin) and Copal (loaded with gentamicin and clindamycin) were insonated and antibiotic release was compared with uninsonated samples. In addition, identical samples were used in combination with cultures of bacteria derived from prosthesis-related infections. The viability of these bacteria was determined with and without ultrasound, using unloaded Palacos R as a control. There was a trend of increased gentamicin release under influence of ultrasound. Clindamycin release from Copal was significantly increased. Ultrasound alone did not affect bacterial viability, but the application of ultrasound in combination with antibiotic-loaded bone cements reduced both planktonic and biofilm bacterial viability. The release of antibiotics from bone cement was increased by the application of ultrasound. Antibiotic release in combination with ultrasound increases the antimicrobial efficacy against a variety of clinical isolates. The enhanced efficacy against bacteria in the biofilm mode of growth, especially against a gentamicin-resistant strain, is clinically important with regard to the treatment of infected joint prostheses. Ultrasound may also be applied in the early postoperative period to prevent infections, because planktonic bacteria present in the wound and wound area due to inevitable contamination during surgery can then be more effectively prevented from forming a biofilm.