One of the major bacterial diseases that affect poultry industry is the Colisepticeamia, caused by Escherichia coli. The present study emphasise on understanding pathogenic potential of the extra-intestinal avian pathogenic Escherichia coli (APEC) isolated from heart blood of infected broiler chickens. The in-vitro pathogenicity studies carried on APEC isolates showed a clear haemolytic pattern on 10% Sheep blood agar and tested positive for biofilm formation. The multidrug resistant pattern of the APEC isolates along with biofilm formation made it difficult to control the disease. The in-vivo pathogenicity tests studied in day old chicks provided an understanding of the pathogenicity of the APEC isolates. The APEC isolates developed infection slowly with clear clinical signs that ends in 100% mortality of the infected chicks. The re-isolation of the injected APEC isolates from heart blood of the dead chicks clearly indicates the significance of virulence posed by the extra-intestinal avian pathogenic E.coli in developing Colisepticaemia.

Keywords: Escherichia Coli; APEC; Pathogenicity; Haemolysin; Biofilm.