Serological and Molecular Typing of Avian Pathogenic E. Coli Originating from Outbreaks of Colibacillosis in Chicken Flocks

Avian pathogenic Escherichia coli (E. coli) is the etiological agents of colibacillosis, which is one of the principal causes of morbidity, mortality in poultry worldwide and responsible for significant economic losses to the poultry industry. Some outbreaks consistently associated with specific serotype, O111 causing mortality, septicemia and polyserositis with the chickens. Detection of Shiga toxin1, Shiga toxin 2 and Intimin genes that encode virulence factors, by multiplex PCR is an efficient method for identifying virulent strains of isolated E. coli. The objective of this study was serotyping of isolated E. coli, measurement of cytotoxicity of E. coli on Vero cell culture, detection of Shiga toxin1, Shiga toxin 2 and Intimin genes of isolated E. coli by using of Polymerase Chain Reaction. E. coli isolates was recovered from 510 samples with overall prevalence 75.2 %. The most prevalent E. coli serovar isolates recovered from different sources of poultry broiler farms were Untypable E. coli serovare, followed by O26, then O2, O124, O125, and O115. Isolated E. coli caused third degree of the cytopathic effect of Vero cell sheet. Out of 20 E. coli isolates recovered from various broiler samples, 5 isolates were positive for Shiga toxin 1 (Stx1) gene, 3 for Intimin gene, and 3 were positive for the Shiga toxin 2 (Stx2) gene.