Abstract / Summary
BackgroundPoultry-associated Escherichia coli can harbor clinically relevant antimicrobial resistance determinants, but the clonal and mobile-genetic backgrounds of β-lactam resistance remain incompletely characterized in Central European production systems. We investigated a phenotypically ESBL-suspect collection of 87 E. coli isolates recovered from tracheal and cloacal samples collected on 23 commercial chicken farms in Hungary between 2022 and 2023.MethodsAntimicrobial susceptibility testing was integrated with whole-genome sequencing, allele-level resistance-gene identification, Achtman multilocus sequence typing, predicted plasmid reconstruction, pan-genome analysis and recombination-filtered core-genome phylogenetics.ResultsPhenotypic ESBL production was confirmed in 19/87 isolates (21.8%). The principal ESBL alleles were blaCTX-M-1 (11/87) and blaCTX-M-15 (3/87), while blaCMY-2 was detected in four isolates. Complete Achtman sequence types were assigned to 44 isolates, representing 30 sequence types. Ten of 11 blaCTX-M-1 occurrences were computationally assigned by MOB-suite to predicted conjugative IncI-gamma/K1 plasmid bins. The recombination-filtered phylogeny resolved multiple distinct lineages, showing that ESBL positivity and CTX-M carriage were not restricted to a single clone.ConclusionThese findings indicate that ESBL- and AmpC-associated resistance occurred across diverse chicken-derived E. coli backgrounds and was frequently associated with predicted plasmid contexts.