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

Escherichia coli (E. coli) is a widespread avian pathogen, usually considered as secondary pathogen for different infectious agents causing huge financial losses in the poultry industry. A total of 18 flocks out of 30 broiler flocks (60%) were positive for E. coli infection. Based on the Congo red (CR) binding assay, 15 flocks out of 18 were identified as pathogenic E. coli (83.3%) and 3 flocks appeared as non-pathogenic 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 to 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 viruhave 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, 20% were positive for 4 resistance genes and 20% were positive for resistance 3 genes. We can conclude that E. coli continues to threaten the poultry industry and further studies are recommended to find 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.