Background: Avian-pathogenic Escherichia coli (APEC) are pathogenic strains of E. coli that are responsible for one of\nthe most predominant bacterial disease affecting poultry worldwide called avian colibacillosis. This study describes\nthe genetic determinants implicated in antimicrobial resistance among APEC isolated from different broiler farms in\nEgypt.\nMethods: A total of 116 APEC were investigated by serotyping, antimicrobial resistance patterns to 10 antimicrobials,\nand the genetic mechanisms underlying the antimicrobial-resistant phenotypes.\nResults: Antibiogram results showed that the highest resistance was observed for ampicillin, tetracycline, nalidixic\nacid, and chloramphenicol. The detected carriage rate of integron was 29.3% (34/116). Further characterization of\ngene cassettes revealed the presence gene cassettes encoding resistance to trimethoprim (dfrA1, dfrA5, dfrA7, dfrA12),\nstreptomycin/spectinomycin (aadA1, aadA2, aadA5, aadA23), and streptothricin (sat2). To our knowledge, this the first\ndescription of the presence of aadA23 in APEC isolates. Analysis of other antimicrobial resistance types not associated\nwith integrons revealed the predominance of resistance genes encoding resistance to tetracycline (tetA and tetB),\nampicillin (blaTEM), chloramphenicol (cat1), kanamycin (aphA1), and sulphonamide (sul1 and sul2). Among ciprofloxacin-\nresistant isolates, the S83L mutation was the most frequently substitution observed in the quinolone resistancedetermining\nregion of gyrA (56.3%). The blaTEM and blaCTXâË?â??MâË?â??1 genes were the most prevalent among APEC isolates\nproducing extended-spectrum beta-lactamase (ESÃ?²L).\nConclusions: These findings provided important clues about the role of integron-mediated resistance genes\ntogether with other independent resistance genes and chromosomal mutations in shaping the epidemiology of\nantimicrobial resistance in E. coli isolates from poultry farms in Egypt.
Loading....