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. 2025 May 31:18:2765-2777.
doi: 10.2147/IDR.S521802. eCollection 2025.

Antimicrobial Resistance and Genomic Characterization of Salmonella Serovars Typhimurium and 4,[5],12:i:- in Huzhou, China

Wei Yan  1 , Lei Ji  1 , Yunfeng Zha  1 , Fenfen Dong  1 , Deshun Xu  1
Affiliations

Antimicrobial Resistance and Genomic Characterization of Salmonella Serovars Typhimurium and 4,[5],12:i:- in Huzhou, China

Wei Yan et al. Infect Drug Resist. .

Abstract

Objective: Salmonella serovar Typhimurium (S. Typhimurium) and its monophasic variant, Salmonella 4,[5],12:i:-, have become two of the most frequently isolated serovars worldwide, in both humans and animals. This study investigated the antimicrobial resistance and genomic characteristics of these two serovar Salmonella.

Methods: Between 2021 and 2023, a total of 90 S. Typhimurium and Salmonella 4,[5],12:i:-were collected from clinical and food samples in Huzhou. Their antimicrobial resistance phenotype and genes, virulence genes, and phylogenetic relationship were analyzed.

Results: Salmonella 4,[5],12:i:-, which all belong to ST34, has become the main serotype of Salmonella isolated in Huzhou instead of S. Typhimurium. Notably, we observed a higher incidence of infections among the young population (<5 years old). The 90 Salmonella isolates were mainly resistant to tetracycline (94.4%), ampicillin (72.2%), and trimethoprim/sulfamethoxazole (70.0%), with multidrug resistance (MDR) rates as high as 93.3%. Genome sequencing indicated that these isolates possessed 39 antimicrobial resistance genes and 184 virulence genes.

Conclusion: This research enhances our understanding of S. Typhimurium and Salmonella 4,[5],12:i:- infections, which is helpful to guide clinical responses.

Keywords: Salmonella typhimurium; antimicrobial resistance; monophasic variant; multidrug resistance; whole genome sequencing.

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Conflict of interest statement

The authors declare no competing interests in this work.

Figures

Figure 1
Figure 1
Epidemiological information regarding the 90 isolates in this study: (a) number of isolates in each age group; (b) composition ratios of serotypes in each age group. (c) composition ratios of ST types in each age group; and (d) composition ratios of sex in each age group.
Figure 2
Figure 2
Annotation heatmap of AMR genes among 90 isolates.
Figure 3
Figure 3
Annotation heatmap of virulence factors among 90 isolates.
Figure 4
Figure 4
Core genome SNP-based phylogenomic tree of all 90 Salmonella isolates.
See this image and copyright information in PMC

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