Genomic Relatedness, Inferred Transmission Dynamics, and Antimicrobial Resistance of Salmonella enterica Serotype Mbandaka: A Global Genomic Epidemiology Study

Salmonella enterica serotype Mbandaka has emerged as a significant foodborne pathogen in poultry, posing increasing public health risks through its zoonotic transmission from poultry sources to humans, yet critical gaps remain in understanding its transmission inter-host transmission and antimicrobial resistance (AMR) mechanisms within the poultry industry. In this study, we addressed these knowledge gaps by conducting a comprehensive genomic analysis of 1813 S. Mbandaka genomes, including genotyping, phylogenetic reconstruction, and pangenome analysis. The results revealed that S. Mbandaka exhibits a global distribution pattern, with sequence type 413 (ST413) representing the dominant lineage. Phylogenetic analysis revealed frequent close genomic relatedness between human and poultry-derived strains (SNP ≤ 10), suggesting poultry as a potential major zoonotic reservoir for human S. Mbandaka infection. Furthermore, close genetic relationship was also detected among the human-derived strains, suggesting the potential community spread. In addition, genomic analysis indicated an increase over time in the number of antimicrobial resistance genes (ARGs) detected per genome, frequently associated with plasmids and insertion sequences (ISs). Notably, the ARGs significantly enriched in Chinese strains were primarily associated with the Col(pHAD28) plasmid. Comparative analysis demonstrated that the ARG profiles of S. Mbandaka were similar to those of other Salmonella serovars, suggesting the potential for cross-species transmission. In conclusion, these findings represent a large-scale retrospective genomic analysis of publicly available whole-genome sequences and elucidate the transmission dynamics and AMR mechanisms of S. Mbandaka in poultry, providing insights into its risks to poultry production and public health while guiding the development of targeted prevention strategies for the poultry sector.