Prevalence and Antimicrobial Resistance of Escherichia coli Isolated from Chicken Carcasses in Romania: Zoonotic Potential and Public Health Impact

Antimicrobial-resistant bacteria associated with poultry production pose an ongoing challenge for food safety and veterinary public health. The present study evaluated the prevalence, antimicrobial resistance phenotypes, and selected resistance genes of <i>E. coli</i> recovered from broiler chicken carcasses and cecal content in Romania. Over a 12-month period in 2024, a total of 444 samples were collected, including 300 carcasses obtained from slaughterhouses and retail outlets and 144 cecal samples collected at slaughterhouses. Isolates were recovered using standard microbiological procedures and confirmed through biochemical and automated identification systems. Antimicrobial susceptibility was assessed using a minimum inhibitory concentration-based automated platform, and extended-spectrum β-lactamase (ESBL) production was evaluated phenotypically. Target resistance genes were investigated by PCR. <i>E. coli</i> was identified in 36.0% of carcass samples and 64.6% of cecal samples. High resistance rates were observed for tetracycline (82.6%), ampicillin (68.3%), and trimethoprim-sulfamethoxazole (61.2%), while multidrug resistance occurred in 34.3% of isolates. ESBL production was detected in 11.1% of carcass isolates and 11.8% of cecal isolates and was associated with the presence of <i>bla</i>CTX-M. Additional resistance determinants, including <i>bla</i>TEM, <i>tet</i>A, <i>tet</i>B, <i>sul</i>1, <i>dfr</i>A1, and <i>aad</i>A1, were widely distributed among isolates from both sources. The results suggest that poultry carcasses may contribute to the dissemination of resistant and ESBL-producing <i>E. coli</i>, reflecting intestinal carriage and contamination during processing. Strengthened antimicrobial stewardship, systematic resistance monitoring, and improved hygiene practices throughout the poultry production chain are essential to reduce the public health impact of resistant bacteria.