Phenotypic and genotypic characterization of antimicrobial susceptibility of avian pathogenic Escherichia coli isolated from broiler chickens

Aim: Avian pathogenic Escherichia coli (APEC) is pathogenic strains of E. coli that are responsible for one of the most common bacterial diseases affecting poultry worldwide. This study was designed to determine the occurrence, antibiotic resistance profile, and antibiotic resistance genes of E. coli isolated from diseased and freshly dead broilers. Materials and Methods: In that context, a total of 200 broilers samples were examined by standard microbiological techniques for isolation of E. coli, and tested for their antimicrobial susceptibility against 15 antimicrobial agents using disc diffusion method. In addition, E. coli isolates were screened by multiplex polymerase chain reaction for detection of a number of resistance genes including aadA1 gene encodes streptomycin/neomycin, tetA encodes resistance to tetracycline, sul1 encodes sulfonamides, and beta-lactamase encoding genes (bla(TEM) and bla(SHV)). Results: A total of 73 (36.5%) isolates were biochemically identified as E. coli strains. O78, O2, and O1 are the most prevalent serotypes detected. E. coli displayed a high resistance against penicillin (100%), followed by cefepime (95.8%) and a low resistance to norfloxacin (36.9%), and chloramphenicol (30%). Depending on the results of PCR, sul1 gene was the most predominant antibiotic resistant gene (87%) followed by bla(TEM) (78%), tetA genes (60%), and aadA (54%). However, bla(SHV) had the lowest prevalence (23%). Conclusion: The obtained results demonstrated the importance of studies on APEC and antibiotic resistance genes in our region which associated with intensive poultry industry, aiming to acquire preventive measures to minimize losses due to APEC and associated multidrug-resistance and resistance genes that of high significance to the rational use of antibiotics in clinical and public health.