Comparison between avian pathogenic (APEC) and avian faecal (AFEC) Escherichia coli isolated from different regions in Brazil.

Detection and analysis of virulence-associated genes (VAGs) of avian pathogenic Escherichia coli (APEC) may be helpful to distinguish pathogenic from commensal faecal strains (AFEC). The aim of this study was to characterise 120 isolates of avian Escherichia coli, comprising 91 APEC (from diseased birds) and 29 AFEC (from healthy chickens), collected in Brazil. Phylogenetic analysis and in vivo pathogenicity testing was performed on 38 VAGs. The VAGs iucD, iutA, iroN, fepC, ompT, cvi and hlyF were statistically associated with medium and high pathogenicity (MP/HP) strains. A minimal group of seven VAGs may be required to accurately discriminate pathogenic and non-pathogenic avian strains of E. coli in Brazil.