QUORUM SENSING AND BIOFILM FORMATION IN AVIAN PATHOGENIC ESCHERICHIA COLI  (APEC)

Victor Gonçalves Maturana (UNICAMP); Franciely Paula Toniolo de Paiva (Instituto Butantan); Fabrício Hebert Culler (Instituto Butantan); Marcelo Palma Sircili (Instituto Butantan); Wanderley Dias da Silveira (UNICAMP)

Introduction. The Brazilian avian industry, an important economical segment, is harmed by infectious processes that result in high death rates and condemnation of the carcasses, besides low growing rates. Among the pathogenic microorganisms Escherichia coli plays an important role. The strains of this bacterium involved in avian diseases are collectively denominated APEC (avian pathogenic Escherichia coli) and colibacillosis is the term used to designates the disease onset. Objectives. In this work we investigated the capacity of biofilm formation and the presence of quorum sensing signal molecule, AI-3, in different APEC strains (62 strains isolated from chickens with disease clinical signals, and healthy birds, for comparison). Methods. The biofilm formation was detected through the crystal violet technique. The presence of quorum sensing signal molecule, AI-3, was investigated through the ¦Â -galactosidase assay, using a human E. coli strain containing the lacZ::LEE1 fusion as reporter gene. This sample was grown in pre-conditioned culture media obtained from the APEC strains to early exponential phase (OD₆₀₀ ¡Ü 0.2). These cultures were diluted 1:10 in Z buffer (Na2HPO4, 0.06 M; NaH2PO4, 0.04 M; KCl, 0.01 M; MgSO4, 0.001 M; ¦Â-mercaptoethanol, 0.05 M) and assayed for ¦Â-galactosidase activity by using o-nitrophenyl-¦Â-Dgalactopyranoside as substrate. The yellow color indicating ¦Â-galactosidase activity was red in 420¦Çm and the results analyzed by Miller Units. Results. In regard to the crystal violet staining, we observed presence of high absorbance, and therefore high rates of adhesion to the plate, suggesting biofilm formation, in strains from both studied groups, pathogenic and commensal strains. In relation to the ¦Â-galactosidase assays, we observed that the pre-conditioned media were capable of induce a higher activity of the enzyme, indicating the presence of AI-3. Discussion.  In this study, we suggest the existence of biofilm formation among commensal and pathogenic avian E. coli, and presence of quorum sensing system, specifically of AI-3 based system.