Silicone-covered metal stents: an in vitro evaluation for biofilm formation and patency

Self-expanding metal stents are being used more commonly to prevent biliary tract obstruction. Silicone-covered self-expanding metal stents (Wallstent, Schneider, Inc.) have been developed to prevent tumor ingrowth. Biofilm formation and occlusion material in silicone-covered self-expanding metal stents compared to standard polyethylene stents were examined in an in vitro model. Matched pairs of polyethylene and silicone-covered metal stents were perfused with infected bile for 8, 12, and 16 weeks at a rate of 0.5 cc/min at 37 degrees C. Two reservoirs fitted with silicone-covered metal stents had ampicillin/sulbactam added and were perfused for 16 weeks. The stents were then analyzed by scanning electron microscopy and light microscopy for biofilm formation and presence of occlusion material. The two ampicillin/sulbactam-treated stents showed no biofilm formation. Biofilm was seen on all of the remaining stents. There was a difference in occlusion thickness between the 8- and 16-week polyethylene stents, and no difference between the biofilm thickness at 8, 12, or 16 weeks in the silicone-covered metal stents. Silicone-covered self-expanding metal stents will likely extend patency rates in malignant obstructive jaundice by providing a larger lumen for bile flow and allowing cyclical antibiotics to prevent bacterial biofilm formation.