Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avian species. Virulence-associated genes (VAGs) and pathogenicity islands (PAIs) in APEC play a crucial role in the pathogenicity of this bacterium, leading to severe disease in chickens. In this study, multiplex PCR (mPCR) and PCR reaction were established to identify virulence-associated genes in Escherichia coli (E. coli), including adhesin-related genes (eaeA and tsh), iron acquisition genes (fyuA, iroN and iutA), toxin-related gene (hlyF) and protectins genes (iss and ompT). The results showed that 42 out of 100 (42%) samples were positive for E. coli. The isolated E. coli strains exhibited several biological characteristics, including gram staining, H2S production, indole production, urease, catalase and oxidase tests, as well as the fermentation in TSI medium, consistent with previous studies on E. coli. When evaluating the frequency of virulence-associated genes in E. coli, the ompT gene showed the highest frequency at 90.5%, followed by iutA (85.7%), hlyF (78.6%), iss (64.3%), iroN (61.9%), fyuA (40.5%), tsh (23.8%), and eaeA (16.7%). Among the 42 APEC strains, 33/42 (78.6%) strains harboured combinations of 4 to 7 virulence-associated genes and were classified as APEC, whereas 9/42 (21.4%) isolates carried only a single virulence gene. The biochemical characteristics observed in the APEC isolates were comparable to those reported for the reference strain Escherichia coli ATCC® 25922™.
