extended-spectrum β–lactamase producing avian escherichia coli isolated from broilers in hamedan, iran

Avian collibasilosis causes morbidity, mortality, and significant economic loss in the poultry industry. avian-pathogenic escherichia coli (apec) is the main etiological agent of collibasilosis. apec is recognized as a zoonotic pathogen and act as reservoir for antimicrobial-resistance genes (args) transmission to humans via the food supply. in this context, the extended spectrum β-lactamases (esbl) producer is increasing among avian e. coli. the present study aims to investigate the prevalence of esbl producer among 100 apec strains, isolated from broiler chickens with colibacillosis, and 100 avian- faecal escherichia coli (afec) strains isolated from apparently healthy broilers, in the hamedan, iran. the esbl producer avian e. coli strains were determined by double-disk synergy test using ceftazidime (30 μg) and cefotaxime (30 μg) disks and confirmed by combined disk diffusion test using clavulanic acid according to the clsi guidelines. besides, the presence of the five args responsible for resistance to β-lactamases antibiotics including blatem, blashv, blactx-m, blaoxa, and blafox, among esbls producer apec isolates (n= 40) and afec isolates (n= 51) were assayed by pcr. the antibacterial susceptibility test results showed 40 (40%) of apec strains and 51(51%) of afec strains were phenotypically identified as esbls producer. the predominant β-lactamases arg was blatem (34/40, 85%), followed by blactx-m (2/40, 5%) and blaoxa (1/40, 2.5 %) among apec strains. in afec strains, the frequencies of the β-lactamases arg were blatem (37/51, 72.5%), blactx-m (5/51, 10%) and blaoxa (2/51, 3.9 %). the blaoxa, and blafox genes were not detected in the apec and afec strains. the present study findings highlight the emergence of esbls producing avian e. coli and incidence of β-lactamases args among these isolates in broilers in iran, therefore applying precise antibiotic stewardship, and prevention strategies are suggested as an essential tool to decrease esbls producer avian e. coli.