Molecular Identification of Resistance and Pathogenicity Genes of E. coli Isolated From Broiler Chicken Farms

Escherichia coli (E. coli) is a widespread avian pathogen and usually is considered as a secondary pathogen for different infectious agents causing huge financial losses in the poultry industry. Thus, the current works aim to molecular detection of resistance and pathogenicity genes of E. coli isolated from broiler chicken farms. A total of 18 flocks out of 30 broiler flocks (60%) were positive for E. coli infection. On the base of the Congo red (CR) binding assay, 15 flocks out of 18 were identified as pathogenic E. coli (83.3%) and 3 flocks appeared as nonpathogenic E. coli (16.6%). All pathogenic E. coli were subjected to in vitro antibiotic sensitivity testing to select the most resistant isolates. Ten pathogenic E. coli isolates representing ten different broiler flocks were subjected for molecular identification via polymerase chain reaction (PCR) for both resistance and virulence genes. The most predominant isolated serotypes were O91, O128, O78, O124, O2 and O44. These strains were related to EHEC, EPEC, ETEC, and EIEC. These E. coli isolates are multidrug resistant (MDR) to extensively drug -resistant (XDR). The virulence genes tsh, papC, iss, iutA, and hlyF were detected in 50% of isolates having 5 genes and 50% having 4 genes. All the tested isolates showed MDR genes 60% of isolates were positive for 5 resistance genes and 20% were positive for 4 resistance genes and 20% were positive for resistance 3 genes. We can conclude that E. coli continues to threaten poultry industry and further studies are recommended to found safe antibiotic natural alternatives to overcome E. coli MDR existing strains side by side with strengthening the bird's immunity and application of strict hygienic measures.