A dynamic in vitro model for evaluating antimicrobial activity against bacterial biofilms using a new device and...

The activity of daptomycin compared to vancomycin against Staphylococcus epidermidis-biofilms on intravascular catheters has been evaluated using the new Sevilla device that enables to use medical grade-catheters, in an in vitro model that simulates the in vivo conditions. S. epidermidis-biofilms were obtained on polyurethane catheter segments using the Sevilla device linked to a continuous culture system for 24 h. To assess the antimicrobial activity, at this time the continuous culture system was changed to therapeutic antimicrobial concentration solutions for 48 h. At each 24 h interval time, catheter segments were taken out, washed and sonicated. Viable adherent bacteria were determined by agar plating. Data of surviving bacteria numbers attached to the catheter surface obtained with the Sevilla device showed a very good reproducibility. Daptomycin showed a good activity against S. epidermidis-biofilm on polyurethane catheter surface. After 48 h exposure to daptomycin, surviving adherent bacteria were reduced by 4 log compared to the control with no antimicrobial. Using the same model, vancomycin reduced bacterial survival by only 1.3 log. The Sevilla device enables antimicrobial agent activity against bacterial biofilms grown on the external surface of catheters used in clinical practice to be evaluated. The model used replicates as closely as possible the biofilm formed in a highly standardized way. Using this model, daptomycin demonstrates potent in vitro activity against S. epidermidis-biofilm on a polyurethane catheter; this activity was greater than that showed by vancomycin.