Molecular Characteristics and Zoonotic Potential of Salmonella Weltevreden From Cultured Shrimp and Tilapia in Vietnam and China.

SalmonellaWeltevreden is increasingly reported from aquatic environments, seafood, and patients in several Southeast Asian countries. Using genome-wide analysis, we characterizedS. Weltevreden isolated from cultured shrimp and tilapia from Vietnam and China to study their genetic characteristics and relatedness to clinical isolates ofS. Weltevreden ST-365. The phylogenetic analysis revealed up to 312 single-nucleotide polymorphism (SNP) difference between tilapia isolates, whereas isolates from shrimp were genetically more closely related. Epidemiologically unrelated isolates from Vietnam were closely related to isolates from China, e.g., 20 SNPs differences between strains 28V and 75C. In comparison with strains from other parts of the world, our environmental isolates predominantly clustered within the continental South Asia lineage, constituted mostly of strains from human stool with as low as seven SNPs difference, e.g., 30V versus Cont_ERR495254. All sequenced isolates were MLST type ST-365 and contained the major virulence-related genes encoded by theSalmonellaPathogenicity Islands 1-5. Ten of the isolates harbored theIncFII(S) plasmid similar to the virulence genes-mediated plasmid pSPCV ofS.Paratyphi C, and one isolate had theIncQ1 plasmid on the same contig withstrA/B,sul2, andtetA resistance genes similar to theIncQ1 type, pNUC ofS.Typhimurium. A pangenomic analysis yielded 7891 genes including a core genome of 4892 genes, with a closely related accessory genome content between clinical and environmental isolates (Benjaminip> 0.05). In a search for differences that could explain the higher prevalence ofS. Weltevreden in aquatic samples, genomes were compared with those of otherSalmonella entericaserovars.S.Weltevreden revealed specific regions harboringglpX (Fructose-1;6-bisphosphatase; class II),rfbC (dTDP-4-dehydrorhamnose 3;5-epimerase), andcmtB (PTS Mannitol-specific cryptic phosphotransferase enzyme IIA component) involved in carbohydrate biosynthesis pathways. Our study builds grounds for future experiments to determine genes or pathways that are essential whenS.Weltevreden are in aquatic environments and microbial interactions providing survival advantages toS.Weltevreden in such environments.