Genetic and Phenotypic Characterization of a Salmonella Enteritidis ST11 Clinical Isolate Carrying blaNDM-13 in Jiaxing City, China

Background/Objectives: Multidrug-resistant Salmonella enterica serovar Enteritidis, especially those isolated from humans, remains a public concern. In the present study, S. Enteritidis strain 31404 was obtained clinically from a fecal sample of a fifteen-year-old girl, who was positive for blaNDM-13. Methods: Antibiotic susceptibility testing and whole genome sequencing were performed. Core genome MLST and hierarchical clustering (HierCC) were performed using EnteroBase. Population structure analysis of 57 S. Enteritidis isolates collected between 2023 and 2025 in Jiaxing city was conducted. A comparative structure analysis of blaNDM-13-positive plasmids was also performed. Results: S. Enteritidis strain 31404 was resistant to 13 antimicrobial agents. We found that strain 31404 belonged to ST11 and carried resistance genes, such as blaNDM-13, blaCTX-M-14, bleMBL, fosA3, qnrS, and tet (A). blaNDM-13 was located on an IncI1-I (α) plasmid designated as p31404-NDM13. S. Enteritidis isolate 31404 was closely related to PNUSAS514422, which was isolated from the United States in 2025. Comparative genetic environment related to blaNDM-13-positive plasmids available in the NCBI database indicates that ΔTn125-mediated contexts were commonly associated with blaNDM-13. IS1294 (IS91 family), which replaces ISAba125, is likely to mobilize blaNDM-13. Conclusions: The findings in this study provide insights into the molecular characterization and diversification of blaNDM-13. The identification of blaNDM-13-containing transferable plasmids in different serotypes of Salmonella isolates (such as S. Rissen, S. Typhimurium, and S. Enteritidis) in different cities in China highlights the risk of the spread of carbapenem-resistant genes among Salmonella isolates.