Molecular determination of virulence and antimicrobial resistance genes in Escherichia coli recovered from broiler chickens

This study was carried out to detect the prevalence of Escherichia coli (E. coli) strains in Cobb, Sasso, and Balady breeds of broiler chickens using conventional techniques and to evaluate the in-vitro susceptibility of the isolated strains to different antimicrobials. Besides, the presence of some virulence and antimicrobial resistance genes of E. coli strains was molecularly investigated. A total of 400 samples including liver, heart, spleen, lungs, and intestine were collected from freshly dead, diseased, and apparent healthy chickens in Damietta city, Damietta governorate, Egypt. The samples were subjected to conventional isolation and biochemical identification of E. coli and the results revealed a total prevalence of 20.5% (82/400) with the highest isolation rates from freshly dead breeds of chickens. The serological typing showed presence of O86:K61 and O26:K60 E. coli types. The results of the in-vitro antimicrobial susceptibility test of 82 E coli strains revealed high degrees of resistances to cephradin, amoxicillin/clavulanic acid, sulfamethoxazole-trimethoprim, and doxycycline. The virulence genes including phoA, iss, and tsh were detected in 15 of E. coli strains with percentages of 100%, 33.33%, and 13.33%, respectively. Moreover, the results showed presence of blaTEM, sul1, and mcr1 antimicrobial resistance genes in 15 of E. coli strains with a percentage of 33.33% for each gene. In conclusion, E. coli strains are still circulating in chicken flocks causing economic loses and they are resistant to most of the commonly used antimicrobials. Thus, adopting effective intervention strategies and better management systems are very critical to reduce E. coli-related hazards linked to poultry.