Resumo

Extraintestinal pathogenic Escherichia coli (ExPEC) cause urinary tract infections, neonatal meningitis and septicemia in humans. In birds ExPEC strains are denominated avian pathogenic Escherichia coli (APEC) and cause localized or systemic infections, called colibacillosis. Recent studies indicate that members of different ExPEC subpathotypes have similar set of virulence-associated genes, although these strains have been isolated from different hosts and tissues. Until this moment is unknown which factors can define an ExPEC or if it is possible to discriminate one subpathotypes from another. We have a collection of 144 APEC isolates, obtained from lesions of cellulitis from South Brazil; these isolates were characterized in terms of antimicrobial resistance, presence of 34 virulence-associated genes, virulence to one-day-old chicks and clonal relationships by phylogenetic analysis. Timothy Johnson and collaborators proposed, in 2008, the genes iroN, ompT, hlyF, iss and iutA as the minimal predictors of APEC, and they proposed a pentaplex PCR as a rapid diagnostic tool to identify if a strain is an APEC or not. Therefore, we used the pentaplex PCR for these genes to validate it as a rapid diagnostic tool for APEC strains for isolates from South Brazil. Seventy-nine percent of the isolates have the 5 genes, 13% have 4 genes, 6% have 3 genes and 2% have none of the genes. No strain presented 1 or 2 genes. These results support the hypothesis that the Pentaplex is a suitable tool to identify APEC strains. However, when we did a statistical analysis we could not correlate the presence of these genes with virulence of the strains to one-day-old chicks (p>0,05 Kruskal Wallis – Square Chi), what suggest that the Pentaplex is not able to predict the degree of virulence of an APEC isolate.