Bacterial biofilm formation and sludge deposition is a recognized cause of biliary stent blockage. Culture of biliary sludge showed a mixed infection with gram+ve and gram-ve bacteria. Broad spectrum antibiotic coverage has been recommended for prophylaxis and prevention of stent blockage. However, animal studies showed that prophylactic ciprofloxacin which selectively suppress the gram-ve bacteria resulted in prolonged stent patency despite the stents being colonized by gram+ve bacteria. In this study, we tested a possible synergistic effect between gram+ve and gram-ve bacteria in adherence and biofilm formation. Method: selected clinical isolates of E. coli and Enterococci were cultured in separate chemostats to acheive a steady growth (106 CFU/ml) for 3 days and then perfused separately through Modified Robins Devices (2 for E. coli and 1 for Enterococci), containing 10 Fr stent pieces. After 48 hours, the Enterococci suspension was perfused via a sidearm attachment to the 2nd MRD (E + En) initially perfused with E. coli. The stents pieces were removed daily and anlaysed by bacteriological culture and electron microscopy for bacterial adherence and biofilm formation. Results: the mean value of the bacteria adhered are expressed as colony forming units (CFU)/sq.cm. Number of bacteria adhered to stents. Single Perfusion Combined Perfusion (E +En) Time (day) E.coli Enterococci E.coli Enterococci 1 1.5×104 No growth N/A N/A 2 8.5×103 No growth N/A N/A 3 3.1×105 No growth 2.3×106 3.5×102 4 4.5×105 No growth 2.5×106 8.1×104 Conclusion: Gram-ve E. coli are more adherent than gram+ve Enterococci. Presence of E. coli facilitates the attachment of Enterococci suggesting that there is a synergistic effect between gram posititve and gram negative bacteria in adherence and biofilm formation. Further study is in progress to determine if selective treatment with antibiotic against gram-ve bacteria is sufficient in preventing stent blockage.
|Original language||English (US)|
|Number of pages||1|
|State||Published - 1996|
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