Phenotypic and genotypic evaluation of ESBL- and AmpC-producing Escherichia coli isolated from chicken distributed in Birjand, East of Iran

The aims of the present study were to detect Escherichia coli in chicken distributed in Birjand, to investigate the prevalence of ESBL and AmpC beta-lactamases producers among them, and to identify their antibiotic resistance patterns. The study was conducted on 150 chicken samples, and the antimicrobial susceptibility patterns were determined by the Kirby–Bauer disk diffusion method. Phenotypic identification of ESBL and AmpC was performed by the combined disk test (CDT). The specific genes of ESBL and AmpC beta-lactamases were detected using two multiplex PCR (m-PCR) assays. According to our results, 116 out of 150 chicken samples were contaminated with E. coli. Moreover, the highest resistance of E. coli isolates was observed to trimethoprim/sulfamethoxazole (46%), ampicillin (40%), and amoxicillin (29.33%). In the molecular confirmation step, among 17 (11.33%) beta-lactamase producers, five samples contained the blaCTX-M14 gene (3.33%), two samples contained blaDHA (1.33%) and blaCTX-M3 gene (1.33%), and just one sample carried blaCMY-2 gene (0.66%). The blaSHV and blaTEM genes were not detected in any strains isolated from the chicken samples. This study showed the contamination of chicken with antibiotic-resistant E. coli. Therefore, it is recommended that veterinarians be more precautious in prescribing antibiotics.