Ukrainian poultry-associated Salmonella Infantis in an international one health genomic context: ST32 predominance and recurrent pESI-like resistance plasmids

Salmonella enterica serovar Infantis is a major poultry-associated foodborne lineage and One Health concern because related strains and resistance plasmids circulate across animal, food, and human compartments. Ukrainian food-derived isolates remain underrepresented in international genomic surveillance despite the country’s importance to poultry production and transnational food supply chains. We investigated 1,267 poultry meat and poultry-derived semi-finished food samples collected in four Ukrainian regions during 2024–2025. Ninety-six Salmonella isolates were recovered, including 72 initially assigned to serovar Infantis. Of these, 26 recoverable isolates were available for antimicrobial susceptibility testing and long-read genome sequencing; genome-based typing confirmed 24 as serovar Infantis, including 23 ST32 isolates. Although ST32 dominated the analysed collection (23/26), cgMLST revealed multiple internal groups rather than a homogeneous lineage. In an international EnteroBase ST32 context, Ukrainian isolates were embedded within a broader European population, with close relatives among poultry-associated genomes from Portugal and Poland and human-associated genomes from the United Kingdom. Acquired antimicrobial resistance gene diversity was predominantly plasmid-associated, including ant(3'')-Ia, sul1, tet(A), dfrA14, aph(3')-Ia, blaTEM-1B, lnu(G), bla CTX-M-3 , and qnrS1 , whereas chromosomal resistance was limited to aac(6')-Iaa and fosA7 . The plasmid landscape was dominated by a conjugative IncFIB-associated AC358 group comprising 24 circular pESI-like plasmids with recurrent marker configurations. These findings place Ukrainian poultry-associated S. Infantis within an internationally distributed One Health ST32 continuum and support plasmid-resolved genomic surveillance for linking food-chain monitoring with antimicrobial resistance risk assessment across sectors.