Development of an antimicrobial urinary catheter to inhibit urinary catheter encrustation

Background: Encrustation of urinary catheters is a frequent problem in patients with long-term indwelling catheters colonised with urease-positive bacteria such as Proteus mirabilis. Catheter blockage may follow catheter encrustation, potentially leading to systemic infection. Prevention of encrustation is difficult and avoidance of recurrence often unsuccessful. One possible preventative strategy is to use a catheter with an antimicrobial surface and development and assessment of such a surface was the aim of this research. Methods: Initial experiments assessed the antimicrobial activity of silicone impregnated with plant-derived antimicrobials and triclosan using agar diffusion. The longevity of activity of each antimicrobial silicone was examined over a period of 11 weeks following soaking individual pieces of antimicrobial silicone in an artificial urine solution before using agar diffusion to test remaining antimicrobial activity. Live/Dead staining of bacteria colonising the surface of each antimicrobial silicone was employed to determine the bactericidal properties of each antimicrobial silicone. Selected antimicrobial silicones were subsequently evaluated for their ability to prevent catheter encrustation in an in vitro bladder model. Results: Results showed that antimicrobial activity was obtained using 1% triclosan-impregnated silicone and that this antimicrobial activity was long-lasting (up to 11 weeks). Use of a dip coat silicone formulation, containing 0.2% triclosan, proved effective at delaying catheter encrustation with P. mirabilis metabolites in vitro. In 8 out of 13 independent experiments using dip-coated catheters, no catheter blockage occurred over 7 days, whilst all control catheters blocked during this period. Only on one occasion was delayed encrustation not evident with the treated catheters. Conclusions: In summary, a dip-coat silicone containing triclosan proved effective in preventing in vitro catheter encrustation caused by P. mirabilis infection. Further studies with triclosan silicone dip coat formulation are warranted, including those that investigate potential host cell toxicity and long-term benefits following its application to indwelling urinary catheters in clinical settings.