Comprehensive Genetic Characterization of Salmonella enterica Serovar Gallinarum Biovar Gallinarum from the Poultry Industry in South Korea

Salmonella enterica subsp. enterica serovar Gallinarum biovar Gallinarum (SG) causes fowl typhoid, an important poultry disease, but the genetic diversity and phylogenetic relationships among Korean SG isolates remain insufficiently investigated. We analyzed 26 Korean SG isolates collected between 2002 and 2026 and compared them with 57 publicly available SG genomes from other countries using whole-genome sequencing. Using a cutoff of 100 core-genome single-nucleotide polymorphisms, 83 isolates were classified into eight clusters and ten singletons, with all Korean isolates assigned to the same cluster. Five sequence types (ST78, ST331, ST13540, ST14504, ST14529) were identified. ST78 was predominant, whereas ST14504 and ST14529 were identified exclusively among Korean isolates. Bayesian phylogenetic analysis estimated the time to the most recent common ancestor of the Korean isolates to be approximately 1990. Genomic analyses revealed differences in Salmonella pathogenicity islands, virulence genes, plasmid replicons, antimicrobial resistance genes, and quinolone resistance-determining region mutations. A resistance profile comprising aac(3)-VIa, aadA1, sul1, and qacEΔ1 was observed exclusively in 12 Korean isolates; of these, eleven harbored only the IncFII(S) plasmid replicon, and IncX1 was also detected in one isolate, together with blaTEM-1B and tet(A). These findings provide valuable genomic and epidemiological insights into SG and may contribute to improved control of fowl typhoid.