A One Health Comparative Study of MDR Escherichia coli Isolated from Clinical Patients and Farm Animals in Satu Mare, Romania

<b>Background/Objectives</b>: Multidrug-resistant (MDR) <i>Escherichia coli</i> is a critical One Health challenge, with rising resistance in both humans and animals. The present study aimed to compare antimicrobial resistance (AMR) profiles of <i>E. coli</i> isolates from hospitalized patients and food-producing animals in Satu Mare, a county located in northwestern Romania. <b>Methods</b>: Between 2022-2023, 701 samples were collected, leading to 571 non-duplicate <i>E. coli</i> isolates (420 human, 151 animal). Human strains were recovered from 21 hospital departments and originated from feces, urine, blood, sputum, ear secretions, cerebrospinal fluid, purulent wound secretions, and puncture fluids. Animal isolates were obtained from ceca collected at local slaughterhouses serving farms in north-west Romania, including samples from turkeys, broilers, and pigs. Antimicrobial susceptibility testing was performed against eight antimicrobials (amikacin, ampicillin, cefotaxime, ceftazidime, cefepime, ciprofloxacin, gentamicin, sulfamethoxazole/trimethoprim) using standardized methods. Resistance classification followed international definitions of MDR. Statistical associations between host species and resistance were assessed with chi-square tests. <b>Results</b>: Resistance levels were consistently higher in <i>E. coli</i> strains isolated from animals compared with those from humans (<i>p</i> < 0.05). Among human isolates, resistance to ampicillin (41.9%), ciprofloxacin (41.4%), and sulfamethoxazole/trimethoprim (45.7%) approached, but did not exceed 50%. In contrast, <i>E. coli</i> strains recovered from animals showed markedly higher resistance, exceeding 50% for ampicillin (78.8%), ciprofloxacin (65.6%), and cefotaxime (55.0%). Amikacin retained full activity against all animal isolates, whereas 2.8% of human strains were resistant. Overall, multidrug resistance (MDR) was observed in 70.0% of <i>E. coli</i> isolates from humans and 79.7% from animals, with the highest resistance burden in pig-derived isolates. <b>Conclusions</b>: The study underscores the veterinary sector as a key contributor to the maintenance and spread of MDR <i>E. coli</i>. Even in clinically healthy animals, resistance levels exceeded those observed in human isolates. These findings emphasize the need for coordinated One Health monitoring and stricter antimicrobial use policies in livestock to reduce transmission risks across human and animal populations.