Background: Bacterial attachment plays an important role in the initiation of biliary sludge formation and stent blockage. In vitro studies were conducted to determine the effects of adherence factors, namely pili and glycocalyx production, and culture media, including brain heart infusion broth, modified Vogel and Bonner medium, and human bile, on the adherence of Escherichia coli to plastic stents. Methods: Clinical isolates of E coli with different adherence mechanisms, that is, piliated (P+) or nonpiliated (P-), glycocalyx producing (G+) and nonglycocalyx producing (G-), were obtained from clogged stents. Adherence studies were conducted by using the modified Bobbins device, and stents were removed at regular intervals to determine the number of attached bacteria/cm2 with the viable plate count method. Polyethylene stents were used to compare the adherence curves of E coli with different adherence factors in brain heart infusion broth. The effects of different culture media on the adherence of P+G+ E coli to polyethylene stents were determined. In addition, the adherence of P+G+ E coli to different plastics in brain heart infusion broth and human bile was compared. Results: P+G+ E coli adhered better than P-G+ and P-G- E coli to polyethylene stents. Modified Vogel and Bonner medium, which stimulates glycocalyx production, enhanced the attachment of P+G+ E coli, whereas human bile decreased E coli attachment to polyethylene stents, despite an increase in glycocalyx production. There was a difference in adherence of P+G+ E coli to polyethylene, polyurethane, and Teflon stents in brain heart infusion broth, but the differences were nullified in the presence of human bile. Conclusions: P+G+ E coli with both adherence factors adhere best to plastic stents. Media such as modified Vogel and Bonner medium that stimulate glycocalyx production also enhance bacterial attachment. The toxic effects of bile salts in human bile on the bacteria might alter the adherence mechanism and reduce E coli attachment.
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