Genetic Characteristics of Multidrug-Resistant Salmonella Isolated from Poultry Meat in South Korea

Given the lack of genetic characterization data for multidrug-resistant (MDR) in South Korean poultry, we analyzed 53 MDR strains from 1232 poultry meat samples (723 chicken, 509 duck) using whole-genome sequencing. Five serotypes were identified: Infantis (30/53, 56.6%), Enteritidis (11/53, 20.8%), Virchow (9/53, 17.0%), Agona (2/53, 3.8%), and Indiana (1/53, 1.9%). Sequence types (STs) included ST32, ST11, ST16, ST13, and ST17, with three major clusters, each having two subclusters. Eight core genome sequence types (cgSTs) were identified: 225993, 2268, 58360, 150996, 232041, 96964, 117577, and 267045. Infantis and Enteritidis had two (117577, 267045) and three (225993, 2268, 58360) cgSTs, respectively, whereas Virchow showed allelic differences in identical cgSTs. The Enteritidis subcluster was classified as chicken or duck. Twenty-eight antimicrobial resistance genes (ARGs), 10 plasmid replicons, 11 pathogenicity islands (SPIs), and 230 virulence genes were identified, showing distinct profiles by cluster and subcluster. Infantis, the primary MDR , carried the IncFIB (pN55391) plasmid, 10-11 ARGs, nine SPIs, and approximately 163 virulence genes. Three major MDR serotypes ( Infantis, Enteritidis, and Virchow) had specific genetic profiles that can inform epidemiological surveillance.