Bacterial biofilm, brown pigment stone and blockage of biliary stents.

Bacterial pathogens gain access into the biliary system by descending via the portal venous circulation or ascending through the sphincter of Oddi in duodenal-biliary reflux. Bacteria thrive as glycocalyx-enclosed microcolonies, coalescing to form an adherent biofilm. The establishment of biofilm is a key event in the formation of biliary sludge and pigment gallstones, and the blockage of biliary stents. The biofilm mode of growth is very effective because it provides bacteria with a measure of protection from antibacterial agents and phagocytic leucocytes. Calcification of the matrix confers further protection for the micro-organisms living inside the biofilm. To date, attempts to prevent blockage of biliary stent have employed physical methods by using large self-expandable stents and stents without side hole. Incorporation of antibiotics within stents has not been successful presumably because bacteria once living in their biofilm are quite resistant to antimicrobial agents. Even the most toxic bile salts have no effect on the biofilm bacteria. Yet, hydrophobic bile salts reduce bacterial adhesion on biomaterial, suggesting that incorporation of such bile salts might prevent the formation of bacterial biofilm.