[Clinical and preclinical efficacy of antimicrobial catheters]

Frequent use of polymeric material for diagnostic and therapeutic use has provoked an increase of so-called polymer-associated foreign body infections. The difficulties in correctly diagnosing catheter-related infections and the necessity to remove the device in case of suspected infection require preventive procedures in the first place. Therefore, several studies have dealt with surface treatment by coating with antibiotics, antiseptics and silver. Some of them remain in clinical trials or are already sold in the USA. Clinical failure of silver-sulfadiazine coated CVCs has been reported recently. Recently a rifampicinminocyclin-catheter has been shown to reduce efficiently material-associated infection in preclinical and clinical studies. Most of the substances retained on catheter surfaces are released only in small quantities resulting in ineffective suppression of bacterial growth. If substantial amounts of antimicrobials are incorporated into the biomaterial, release pattern and killing efficacy of each substance group has to be determined in order to reach bactericidal concentrations in the environment of adherent bacteria. Killing kinetics of antibiotics, antiseptics and silver to bacteria are strongly different. On the one hand killing kinetics of microorganism due to substantial quantities of antiseptics are fast, on the other hand antiseptics destroy structures of both, bacteria and blood cells. Bactericidal concentrations of Ag-ions show fibroblast inhibition. Antibiotics, however, show lowest toxicity due to the specific action to microorganisms. However, sustained release over time is needed to reach bactericidal concentrations, considering the slower bactericidal action of typical antibiotics. Development of allergic reaction is possible for all substances, whereas development of bacterial resistance can be prevented by use of antimicrobial combinations.