Antimicrobial Susceptibility Profiles of Escherichia coli Isolates from Clinical Cases of Chickens in Hungary Between 2022 and 2023

<b>Background</b>: The global spread of antimicrobial resistance (AMR) necessitates collaborative approaches between animals, their environment, and public health sectors, fostering the One Health concept. <i>Escherichia coli</i> (<i>E. coli</i>) is a zoonotic, facultative pathogenic bacterium. Its public health significance underlines the need for the regular monitoring of different strains causing clinical disease, especially in poultry, more specifically in chickens, which have become a critical source of animal protein. <b>Methods</b>: The antimicrobial susceptibility of 133 <i>E. coli</i> strains isolated from clinical cases in large-scale Hungarian poultry between 2022 and 2023 was assessed via the gold-standard minimum inhibitory concentration (MIC) determination, which provides internationally comparable results. <b>Results</b>: Our findings revealed high resistance levels to widely used antibiotics, including amoxicillin (57.9%), neomycin (78.9%), doxycycline (46.6%), and potentiated sulfonamides (43.6%). Resistance to these critically important antibiotics is particularly concerning due to their public health significance. Comparison with regional human resistance data revealed similar patterns for β-lactam antibiotics; however, aminoglycosides, fluoroquinolones, and potentiated sulfonamides exhibited significantly higher resistance levels in veterinary isolates. <b>Conclusions</b>: Our results highlight the importance of routine surveillance, which has both veterinary and public health implications. Future efforts to correlate antibiotic usage with resistance patterns and to elucidate the genetic background of multidrug-resistant strains will further strengthen the One Health approach.