Genotypic and phenotypic characterization of E. coli associated to edema disease in swine

Edema disease affects weaning piglets and is caused by a host adapted Escherichia coli and producer of Stx2e toxin. The edema disease is characterized by swollen eyelids, ataxia, recumbence, convulsions, paralysis, or sudden death. In the present study were evaluated 158 E. coli strains Stx2e toxin gene positive isolated from 62 animals, from 13 swine herds located at Rio Grande do Sul, Santa Catarina, Mato Grosso, Paraná, São Paulo, Goiás and Minas Gerais States. Strains were submitted to resistance profile determination, virulence genes detection, phylogenetic group characterization, toxin expression in Vero cell culture, genotypic characterization through pulsed field gel electrophoresis (PFGE) and single enzyme amplified fragments length polymorphism (SEAFLP). Among the 158 strains stx2e+ were identified 83.5% (132/158) resistant to more than three or more classes of antimicrobials, High levels of resistance were found against tetracycline, sulfonamide and florfenicol. The frequency of virulence genes associated to edema disease as F18 fimbriae, for example, was low in relation to other studies. All 158 tested strains presented Stx2e toxin expression and cytotoxic effect in Vero cell culture. The characterization of phylogenetic groups permitted the distribution of strains in four groups described as follow: group A 27.2% (43/158), group B1 3.8% (6/158), group B2 39.2% (62/158) and group D 29.8% (47/158). The strains were characterized through PFGE and the SE-AFLP, and both techniques presented high discriminatory index (0.98 and 0.99 respectively). The association more frequently in both techniques was observed in relation to animal and herd origin. Despite to belong to one defined pathotype (STEC) and to be highly specialized in relation to host, the swine, it was observed a high variability of genetic and resistance profile among tested E. coli. (AU)