Abstract
Avian Pathogenic Escherichia coli (APEC) infections concern economically the poultry industry inducing different disease syndromes leading to high mortality and condemnations. There is tremendous diversity in O serotypes within even a limited geographic region. It has been reported previously on a live E. coli vaccine’s ability to protect against different O78 APEC in commercial broilers. Due to the diversity of APEC serotypes in the field, this study was conducted to measure that live attenuated E. coli (Poulvac® E. coli) vaccine’s ability to cross-protect against three of the heterologous (non-O78) APEC isolates; O27, O8, and O115 compared to cefotaxime treatment through experimental infections in commercial broiler chickens. While the vaccination gave significant protection against the three serotypes tested there were at least subtle differences between them based on clinical signs, post-mortem lesions and mortality rate for 14 days post-challenge (dpc), E. coli re-isolation and histopathological examination at 4, 10 and 14 dpc., final body weight and feed conversion ratio at 35 days of age.