The current study was carried out to evaluate the phenotypic and genotypic characterization of avian pathogenic Escherichia coli recovered from Riyadh, Saudi Arabia. During the period of 10th February-30th May 2015, 70 E. coli strains were isolated from chicken farms located in Riyadh, Saudi Arabia. All strains were tested phenotypically by standard microbiological techniques, serotyped and the virulence genes of such strains were detected by polymerase chain reaction (PCR). Most of the recovered strains from chickens belonged to serotype O111:K58 25 strains (35.7%), followed by serotype O157:H7 13 strains (18.57%), followed by serotype O114:K90 10 strains (14.29%), then serotype O126:K71 9 strains (12.9%), serotype O78:K80 8 strains (11.43%) and in lower percentage serotype O114:K90 and O119:K69 5 strains (7.14%). The virulence genotyping of E. coli isolates recovered from broilers revealed the presence of the uidA gene in all the field isolates (6 serovars) examined in an incidence of 100%, as well as the cvaC gene was also present in all field isolates (6 serovars), while the iutA gene and the iss gene were detected in 5 out of 6 field serovars in an incidence of 81.43% and 64.29%, respectively. Phenotypical examination of the other virulence factors revealed that 65 isolates were hemolytic (92.9%), as well as 15 isolates (21.42%) were positive for enterotoxin production. Meanwhile, 21 isolates (30%) were positive for verotoxin production, 58 isolates (82.86%) for the invasiveness and 31 isolates (44.29%) for Congo red binding activities of the examined serotypes.
Keywords: Avian pathogenic; Escherichia coli; PCR; Serotyping; Virulence factors.