[en] The avian pathogenic E. coli strains, although considered by almost like opportunist pathogen, represent actually one of the most important cause of economic losses in the poultry sector and is one of the most frequent cause of carcase rejection in the slaughter house. Colibacillosis, which the major way of penetration is the respiratory tract, affect essentially broilers and give variable lesions and manifestations in function of the age of the animals. Actually, some virulence factors have been studied and associated with avian pathogenic E. coli strains : P and F1 fimbriae, hemagglutination, serum resistance, aerobactin system. Recent studies have also showed that other virulence factors (F17 and Afa adhesins) were also present in the avian pathogenic E. coli, but their rule in the pathogenicity must to be established. Because of the diversity of virulence factors and the little of knowledge about us, no vaccine is actually available to protect efficacely poultries against colibacillosis. Thus, the antibiotherapy based on a good diagnostic and a good prevention remained the only things to do in order to overcome the disease, despite the augmentation of antibiotics resistance and the risk of transferring to humans.