Prevalence and Antimicrobial Resistance of ESBL E. coli in Early Broiler Production Stage and Farm Environment in Lithuania

<i>Escherichia coli</i>, a major opportunistic pathogen in chickens, poses a serious threat to poultry production and public health via potential zoonotic transmission of ESBL-producing strains. Therefore, this study aimed to emphasize broilers as early carriers of ESBL <i>E. coli</i> and provide deeper insights into antimicrobial resistance of these bacteria. Prevalence and antimicrobial resistance (MIC) testing of ESBL <i>E. coli</i> in cloacal and environmental samples from one-day-old and five-day-old broilers was conducted on three different growth cycles from a conventional poultry farm in Lithuania. Confirmed prevalence of ESBL <i>E. coli</i> in cloacal samples ranged from 0% to 57.5%, and in environmental swabs from 0% to 25%. All 102 ESBL <i>E. coli</i> isolates were susceptible to meropenem, imipenem, fosfomycin, and colistin. However, 93.14% of the strains were resistant to ceftriaxone (89.06-100%, depending on bacteria isolation source), 97.06% to ciprofloxacin (95.31-100%), and 66.67% to tetracycline (26.09-100%). Additionally, 80.39% of ESBL <i>E. coli</i> strains exhibited multidrug resistance. In total, 23 different antimicrobial resistance profiles were confirmed, with CRO/AMS/AUG/CIP/SXT/TE and CRO/CIP being the most common, detected in 18 of the 102 strains. The detection of widespread antimicrobial-resistant ESBL <i>E. coli</i> in five-day-old broilers emphasizes the need to implement control strategies early in the broiler production cycle.