The aim of this study was to characterize the diversity of Escherichia coli strains involved in the dispersion of virulence genes. 152 E. coli strains originated from dairy cattle environment were evaluated through phenotypic and proteomic assays. These samples were investigated for the presence of virulence genes (eaeA, stxI, stxII, ST, LT, eagg, ial) and biofilm related genes (fimH, csgA, flu). Eighteen profiles were obtained and 30 isolates were selected for macrorestriction assay by Pulsed-Field Gel Electrophoresis (PFGE) technique. PFGE patterns of XbaI-digested performed to determine the clonal relatedness of E coli isolates. A total of 27 pulsotypes of E. coli were identified with a low percentage of genetic similarity (≤68%) demonstrating a high genetic diversity in the isolates tested. Furthermore, the presence of biofilm-associated related gene (fimH) can contribute to the dispersion and persistence of this pathogen into the milk environment. Also, all of the pulsotypes (n = 8) with genetic similarity from 95% were present in milk samples, feces and liner were found in different seasons of the year, sharing at least one gene associated with biofilm formation. So the characterization of the genetic diversity of E. coli is important for understanding its dispersion in order to assist in the implementation of measures to prevent the spread of these agents in milk production environment.
Key words: circulating clones, diversity, Escherichia coli, persistence, Pulsed-Field Gel Electrophoresis (PFGE), virulence gene.
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