Antimicrobial resistance of ESBL and/or AMPC producing Escherichia coli isolated from five-day-old broilers flocks in Lithuanian poultry farm

The high prevalence of ESBL and/or AmpC producing Escherichia coli in broilers can lead to human infection and increasing antimicrobial resistance (AMR) cause a risk for consumer health. Our study of three broiler flocks revealed a high prevalence of ESBL and/or AmpC E. coli in a 5-day-old broilers cloacal samples (up to 57.5%) and environmental swabs (up to 25%). One hundred two ESBL/AmpC E. coli isolates (92 ESBL positive/AmpC negative and 10 ESBL positive/AmpC positive) were tested against 13 antibiotics with E-test strips to determine MIC according EUCAST (2024) and CLSI (2024) guidelines. All examined isolates were sensitive only to meropenem, fosfomycin and colistin, but resistant to at least two of the tested antibiotics. A total of 23 different antimicrobial resistance profiles were observed with the most common profiles (17.65%) as CRO/AMS/AUG/CIP/SXT/TE and a combination of CRO/CIP. Multidrug resistance was confirmed in 80.39% of the tested ESBL and/or AmpC E. coli strains. The high resistance rates of ESBL and/or AmpC E. coli were observed for ceftriaxone (93.1%, MIC range from 2 mg/L to >256 mg/L) and ciprofloxacin (97.1%, MIC range from 0.19 mg/L to >32 mg/L). E. coli isolates from cloacal and environmental samples showed similar AMR profiles to all tested antibiotics except that environmental isolates were 5.9 times frequently resistant to gentamicin in comparison to cloacal isolates (p < 0.05). A high prevalence and antimicrobial resistance of ESBL and/or AmpC producing E. coli in 5-day-old broilers emphasizes the need for strategies to control their spread in the early stages of broiler production.