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Genetic characteristics: A clonal group of serovar Weltevreden isolated in farmed shrimp from Vietnam’s Mekong Delta showed susceptibility to most tested antimicrobials, though some isolates exhibited resistance to florfenicol, chloramphenicol, sulfamethoxazole, or trimethoprim. An However, all serovar Weltevreden isolates (100%) collected from wild geckos in Cambodia, Thailand and Vietnamwere were pan-susceptible. An India study found that all Salmonella Weltevreden strains isolated in their study carried virulence genes associated with Salmonella Pathogenicity Islands (SPIs), including invA/E, orgA, ttrC, ssaQ, mgtC, misL, and spi4D), as well as the enterotoxin gene (stn) and the hyperinvasive locus gene (hilA). With the exception of erythromycin resistance, all strains showed susceptibility to standard antimicrobials used in diarrhea treatment.

All sequenced serovar Weltevreden isolates in a Danish study collected from cultured shrimp and tilapia in Vietnam and China belonged to ST365 and carried key virulence genes located within SPI 1–5. Ten isolates possessed the IncFII(S) plasmid, similar to the virulence-associated plasmid pSPCV found in S. Paratyphi C, while one isolate contained an IncQ1 plasmid co-located with resistance genes (strA/B, sul2, tetA), similar to the IncQ1-type plasmid pNUC in S. Typhimurium. Pangenome analysis identified 7,891 genes, with a core genome of 4,892 genes, showing highly similar accessory genomes between clinical and environmental isolates. Additionally, serovar Weltevreden featured unique genomic regions containing glpX (class II fructose-1,6-bisphosphatase), rfbC (dTDP-4-dehydrorhamnose 3,5-epimerase), and cmtB (mannitol-specific PTS enzyme IIA component), which are involved in carbohydrate biosynthesis pathways.

Zhang et al. revealed that most serovar Weltevreden strains from diarrheal patients in China (97.92%, 94/96) and other global regions (94.97%, 189/199) belonged to ST 365. The remaining strains in their study were identified as ST3771 (n=3), ST22 (n=1), ST155 (n=1), and ST684 (n=1). Additionally, ST365 was commonly found in animals, food, and environmental samples worldwide. These serovar Weltevreden strains harbored multiple virulence genes, and a 100.03-kb IncFII(S) plasmid was frequently present. Removing this plasmid reduced the bacteria's ability to infect Caco-2 cells and C57BL/6 mice. 

Animal reservoir: Wild geckos are likely to be the reservoir for serovar Weltevreden. Serovar Weltevreden was also frequently reported from seafood. 

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