Profiles of virulence-associated genes of avian pathogenic Escherichia coli isolates from chickens with colibacillosis

The colibacillosis caused by avian pathogenic E. coli (APEC) is responsible for a significant loss of productivity and mortality in the poultry industry. The pathogenicity of these bacteria is based on the presence and expression of various virulence factors. In this study, the presence of the 19 virulence-associated genes in APEC was determined using PCR. Among the 118 E. coli isolates from the chickens with colibacillosis, all contained at least one of the 19 genes as approximately 95% of the isolates contained fimC. Interestingly, the clpG gene, which has not been detected in APEC previously, was detected in half of the isolates. The ColV plasmid-associated genes such as colV, tsh, iucC, iucD and iss genes were also detected in 57.6, 55.9, 50.0, 47.5, 47.5 and 41.5% of isolates, respectively. With regard to the fimbrial genes, the papA (14.4%), papC (14.4%) and papG genes (15.2%) were identified at relatively low rates, none of the isolates harbored afa8D, f17A or facA, and only 3 of the isolates (2.5%) contained eaeA. In this study, 94 isolates harbored two or more of the genes, and there were 43 different patterns of gene combination in the isolates. The most common pattern, which was found in 14.4% (17 isolates), was clpG-fimC-iutA-colV-tsh-iucC-iucD-irp2-fyuA-vat-iss. Overall, these results suggest that APEC strains in this area commonly contain multiple virulence factors and approximately half of the APEC strains contained the ColV plasmid-associated genes. Especially, colV and tsh were detected more than half of the isoaltes.