Background: Avian colibacillosis is general term that refers to wide variety of complex syndrome such as pericarditis, peritonitis, airsacculitis, salpingitis and other exteraintestinal disease caused by Avian Pathogenic Escherichia coli (APEC). The pathogenisity of APEC associated with serogroups and virulence factors coded by virulence associated genes (VAG). APEC virulence factors are involved in colonization, adhesion, invasion and survivial of E.coli against host defenses. Among these factors, the fimC gene has important role in the biosynthesis of type 1 fimberiae, an important bacterial adhesion molecule. Most of the APEC strains have Col plasmids that are involved in the establishment of avian infection and encoded by cvaA/B. Another virulence gene is iutA an aerobactinsiderophore receptor gene that, contribute to iron uptake. The aim of this study was to detection of virulence factors genes in Avian E. coli, isolated from suspected broiler to colibacillosis in broiler farms in the Hamedan, West of Iran by multiplex PCR. Method: Avian Escherichia coli strains (n= 100) isolated from suspected broiler to colibacillosis from different poultry flocks in the Hamaden, West of Iran were investigated for the presence of the fimC, cvaA/B and iutA virulence associated genes using multiplex PCR. Results: The multiplex PCR results showed that the iutA, fimC, and cvaA/B virulence associated genes had detection rates of 97%, 85%, and 52% respectively. Half of 100 isolates (50) harbored two VAG and 44 isolates contains all three all three VAG and 7 Isolates had only one VAG. Conclusion: Our results suggest that fimC, cvaA/B and iutA VAG are candidates for predicting the pathogenicity of avian E.coli strains and these genes could be used for future vaccine production against colibacillosis and requires further study. Keywords: Escherichia coli, colibacillosis, virulence genes, Multiplex PCR
