Characterization of E. Coli Associated with High Mortality in Poultry Flocks

Received at: 18/8/2013 Accepted: 23/10/2013 A total of 105 cases of broilers were collected from broiler flocks showing high mortality rates in Sharkia Governorate. E. coli was isolated from 84 (80%) cases. A number of 11 different serotypes were identified, of which O114:K90 was the most detected with 17.9% of the total isolates. While O125:K70, O55:K59, O111:K58 and O26:K60 were identified with the percentages of 14.3%, 14.3%, 10.7% and 10.7%, respectively. Five serotypes (O145:K –, O25:K11, O44:K74, O126:K71, O118:K –) had the same isolation percentage (3.6%). However, serotyping failed to determine 7.1% of the isolates. Studying antibiotic resistance pattern of E.coli isolates revealed that all the isolates demonstrated multidrug resistance pattern. The highest resistance rates were recorded against Doxycyclin (100%), while the resistance against Penicillin, Lincomycin, Nalidixic Acid, Tetracycline and Oxitetracycline was (96.4% each). The highest sensitivity rates were recorded to Colistin (89.3%), Ciprofloxacin (75%) and Gentamycin (50%). 380 bp of the island-associated gene eaeA was amplified by PCR for 14 representative isolates of the different serotypes to estimate their virulence. Quinolone resistance was detected by amplifying 403 bp of the qepA gene (Plasmid-encoded efflux pump gene), 516 bp, 469 bp, 417 bp and 113 bp of the qnrA, qnrB, qnrS and aac(6′)-Ib-cr genes (Plasmid-mediated quinolone resistance genes). Amoxicillin resistance was detected by amplifying 516 bp of the blaTEM gene which encodes the β-lactamases. It was concluded that multiresistant virulent strains of E. coli are circulating in broiler flocks and are implicated in cases of high mortalities causing great economic losses.