Isolation Of Biofilm-Forming Yersinia ruckeri Strains From A Rainbow Trout Farm     Laurent Coquet1, 3, P. Cosette1, 3, L. Quillet2, F. Petit2, G.A. Junter1, 3 and T. Jouenne1, 3   1UMR 6522 CNRS; 2Laboratory of Microbiology, Faculty of Sciences of Rouen, 76 821 Mont-Saint-Aignan; 3IFRMP 23, France     Water, sediment and moss samples were collected monthly in the rearing tank of a French rainbow trout farm from October 1999 to September 2000. Twenty-two isolates of Y. ruckeri were obtained and were confirmed by polymerase Chain Reaction (PCR). A Pulsed Field Gel Electrophoresis (PFGE) realized with three others Y. ruckeri strains as control showed the presence of various strains in the fish farm. The different environmental strains displayed a high ability to adhere on solid supports. This characteristic was correlated with a high flagella-mediated motility of these strains. Sessile cells were more resistant to oxolinic acid than planktonic counterparts. The results demonstrate that the surface colonization of fish farms tanks by Y. ruckeri is a potential source of recurrent infection for extended periods of time.