bated in a 5—10% CO2 atmosphere at 37 ◦C for at least 48 hours. E. Coli: All bacterial strains were stored in brain heart infusion broth with 20% glycerol at -80 ◦C prior to use. In preparation for amplification, bacterial strains were grown on either MacConkey or nutrient agar overnight at 37 ◦C. E. coli strains. DNA extraction: Samples of The tissue followed by DNA extraction by using standard procedure according to manufacturer’s instruction. Polymerase chain reaction (PCR): Methodologies for PCR analysis are described elsewhere Results: All ORT suspicious isolates were negative in PCR. Serotypes of 13 E. coli isolates from flocks’ colibacillosis revealed most to be O2. There were three untypable strains in the present study. Discussion: The purpose of this study was to examine ORT and E. coli from chickens by culture and PCR tests. A better understanding of the virulence mechanisms of the causative APEC strains are needed to guide the development of preventive measures.