evaluation of updated phylogenetic group analysis among extended-spectrum β-lactamase producing and multi-drug resistant escherichia coli isolated from colisepticemia in poultry

Escherichia coli is reported as the most common organism in humans and animals and has been identified as a critical priority bacterium due to antibiotic resistance by world health organization (who). multidrug-resistant (mdr) and extended-spectrum β-lactamase (esbl)-producing e. coli strains have emerged as a significant global health challenge worldwide due to the difficulty in treating related infections. poultry has been recognized as an important reservoir of e. coli and may play a crucial role in transmitting these strains to humans. the objective of this study was to determine the prevalence of esbl-producing and mdr e. coli isolated from poultry and to investigate their association with different phylogenetic groups. the current study was conducted on a collection of 100 e. coli isolates from colibacillosis in poultry. antimicrobial susceptibility testing, esbl production, and the prevalence of esbl-mediated genes (blatem, blashv, blaoxa, and blactx-m) were assessed. phylogenetic groups were analyzed using both the clermont 2013 and 2019 updated methods.  the highest resistance rates were observed against tetracycline (88%), trimethoprim/sulfamethoxazole (86%), and chloramphenicol (70%). the frequencies of esbl production and mdr were 41% and 70%, respectively. the blatem gene was the most prevalent among isolates, with a frequency of 48%. phylogenetic group analysis assigned e. coli isolates to b1 (23%), d (22%), a (10%), g (11%), f (8%), b2 (5%), and c (4%). implementing antimicrobial stewardship is crucial because the circulation of esbl-producing e. coli and mdr isolates poses a significant threat to both human and veterinary medicine. furthermore, our results revealed a notable prevalence of phylogroup g in poultry, which is the first report of this finding in iran.