Antibiotic susceptibility and high prevalence of extended spectrum beta-lactamase producing Escherichia coli in iranian broilers

Extended-spectrum beta-lactamase (ESBL) producing Escherichia coli have rapidly spread worldwide and cause serious threats for public health. The study was conducted to determine the antibiotic resistance and characterization of ESBL producing E. coli strains isolated from broilers in Northern Iran. Antibiotic susceptibility test was done for a total of 100 isolates of E. coli, recovered from 240 broiler fecal samples at the slaughterhouse stage. ESBL production was screened using double-disc synergy test (DDST) and presence of four ESBL genes including bla(PER), bla(VEB), bla(TEM) and bla(CTX) (M) was tested using PCR. Among 100 strains isolated from broilers, 53% were identified as ESBL-producing E. coli. All (100%) ESBL positive isolates were typed according to the presence of one or two ESBL-associated genes. The most prevalent gene among ESBLs was CTX-M (60.3%) and the PER gene was not present among isolates. All isolates in this study were resistant to colistin and nalidixic acid but were 100% sensitive to cefalexin and furazolidone. The results demonstrated the high prevalence of antibiotic resistant and ESBL producing E. coli among broilers which representing the risk of increasing these strains in human infections associated with food animals.