Whole-Genome Sequencing Analysis of Salmonella enterica Serotype Enteritidis Isolated from Poultry Sources in Mongolia

Seung-un Song^1*Tae-Min La¹Taesoo Kim¹Junyoung Kim²Eunkyung Shin²Uyangaa Temuujin³Ji-Yeon Hyeon¹Dong-Hun Lee¹Sang-Won Lee¹

• ¹Konkuk University, Seoul, Republic of Korea
• ²Korea Disease Control and Prevention Agency, Seoul, Republic of Korea
• ³Mongolian University of Life Sciences, Ulaanbaatar, Ulaanbaatar, Mongolia

Salmonella enterica serotype Enteritidis (S. Enteritidis) is a leading foodborne pathogen in associated with poultry products, and the emergence of antimicrobial resistance.Antimicrobial resistance (AMR) in this serotypeS. Enteritidis poses significant a growing public health concern, particularly in regions with expanding increasing poultry trade.Between April and June 2024, we collected 114 poultry meat samples (Mongolian domestic and Chinese imported) from retail markets in Mongolia and isolated 45 S. Enteritidis strains.An antimicrobial susceptibility testing revealed high resistance rates to nalidixic acid (100%), ampicillin (93.3%), and streptomycin (88.9%). was conducted to assess resistance profiles, and whole-genome sequencing (WGS) was performed to characterize resistance genes, plasmid types, and phylogenetic relationships. High resistance rates were observed for nalidixic acid (100%), ampicillin (93.3%), and streptomycin (88.9%). Whole-genome sequencing (WGS) identified key major resistance genes, including including aac(6')-Iaa, aph(3'')-Ib, blaTEM-1B , and sul2. Mongolian domestic isolates additionally harbored clinically significant resistance determinants, such as the extended-spectrum β-lactamase (ESBL) blaCTX-M-14 and plasmid-mediated quinolone resistance (PMQR) qnrS1, both of which are clinically significant. Plasmid replicon typing revealed analysis indicated that IncF was as the most prevalent type across isolatesall samples, while IncI1-α was predominantly found in multidrug-resistant (MDR) domestic strains.with Mongolian isolates carrying the most AMR genes often possessing IncI1-α. Phylogenetic analysis using whole-genome SNPs (wgSNPs) demonstratedconfirmed distinct clustering of domestic and imported strains, with clear differences in AMR gene profiles and plasmid Inc types.that domestic and imported isolates clustered separately, indicating that Chinese S. Enteritidis strains have not yet been introduced into Mongolia's domestic poultry industry. This study represents the first comprehensive analysis of prevalence and resistance mechanisms of S. Enteritidis in Mongolia poultry production.antimicrobial resistance gene and phylogenetics of S. Enteritidis in Mongolian poultry. The findings underscore the necessity of continuous surveillance and the implementation of effective antibiotic stewardship in the poultry production sector.improved biosecurity measures to mitigate the spread of resistant Salmonella strains in the poultry supply chain.