Evaluation of the adhesive capacity of avian pathogenic Escherichia coli by In vivo and In vitro adhesion to surfaces of the chicken respiratory tract

Several pathogenic strains of E. coli were isolated from chickens, quail, Guinea fowls and turkeys with septicaemic lesions of colibaciuosis. These strains had thin pili (fimbriae) when grown at 37°C but not at 18°C. These pili facilitated adherence of the bacteria to chick tracheal epithelial cells both in vitro and in vivo. In this study, adhesiveness of E. coli to chicken tracheal epithelium and lethality assay in one-day old chicks have been studied employing 13 E.coli strains. Adhesive properties were found in 87% of the lethal strains and in only 40% of the intermediate lethal strains. The role of these pili was also examined by comparing chicks infected intratracheally with piliated bacteria (grown at 37°C) and non-piliated bacteria (grown at 18°C). It is suggested that adhesive property of E.coli strains with the help of pili (fimbriae) to the tracheal epithelium may play an important role in the virulence.