Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China

IntroductionMonophasic Salmonella Typhimurium, characterized by the absence of phase II flagellar antigens, has become increasingly prevalent as a foodborne pathogen, raising significant public health concerns due to its multidrug resistance. This study investigated the genomic characteristics and a...

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Main Authors: Yi Shi, Yuguo Liu, Shen Li, Songwen Wu, Guozhu Ma, Yang Luan, Junjun Zhang, Yali Chen, Wanjing Liu, Tuo Shen, Caiqiao Wang, Jiru Xu
Format: Article
Language:English
Published: Frontiers Media S.A. 2025-04-01
Series:Frontiers in Microbiology
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Online Access:https://www.frontiersin.org/articles/10.3389/fmicb.2025.1565631/full
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author Yi Shi
Yi Shi
Yuguo Liu
Shen Li
Songwen Wu
Guozhu Ma
Yang Luan
Junjun Zhang
Yali Chen
Wanjing Liu
Tuo Shen
Caiqiao Wang
Jiru Xu
author_facet Yi Shi
Yi Shi
Yuguo Liu
Shen Li
Songwen Wu
Guozhu Ma
Yang Luan
Junjun Zhang
Yali Chen
Wanjing Liu
Tuo Shen
Caiqiao Wang
Jiru Xu
author_sort Yi Shi
collection DOAJ
description IntroductionMonophasic Salmonella Typhimurium, characterized by the absence of phase II flagellar antigens, has become increasingly prevalent as a foodborne pathogen, raising significant public health concerns due to its multidrug resistance. This study investigated the genomic characteristics and antibiotic resistance profiles of the monophasic Salmonella Typhimurium strains isolated from patients and food sources in Shaanxi Province, China.MethodsA total of 58 strains were collected between 2020 and 2021, with 4 strains isolated from food and 54 from patients. Whole genome sequencing was performed to assess genomic features. Antimicrobial susceptibility was tested against 17 antimicrobial agents using the broth dilution method, while pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing were employed for genetic characterization and epidemiological analysis. Phylogenetic analysis was conducted using single nucleotide polymorphism clustering.Results and discussionOur results revealed that all the strains belonged to the ST34 and did not carry virulence genes on pSLT (NC_003277). There were 12 strains carrying the STM2757 gene. The isolates exhibited a considerable diversity in PFGE subtypes. Phenotypic antimicrobial resistance showed that the strains were most resistant to tetracycline (94.34%; 50/53) and ampicillin (94.34%; 50/53), followed by streptomycin (88.68%; 47/53) and ampicillin/sulbactam (64.15%; 34/53). Resistance gene prediction highlighted the presence of 64 distinct genes, with aac(6’)-Iaa found in all strains (100%) and tet(B) in 93.1% of strains. Notably, the floR gene, relevant for resistance to phenicols, was observed in 44.83% of isolates. Genomic analysis revealed that 96.55% of strains were positive for the sodC1 virulence gene, whereas only 10.34% carried the sopE gene. The most plasmid replicon was IncQ1 (84.48%; 49/58), followed by IncHI2 (32.76%; 19/58) and IncHI2A (32.76%; 19/58). Single nucleotide polymorphism analysis showed that 2 strains were clustered together with SRR17830210 (UK outbreak isolate) with a bootstrap value of 0.949. There were only 12 allelic differences between SNXiAn21SAL011 and the reference strain. Conclusively, the monophasic Salmonella Typhimurium ST34 strains in Shaanxi Province demonstrated unique genomic and antimicrobial resistance traits. This study may help to prevent outbreaks and rationalize salmonellosis antimicrobial therapeutics.
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spelling doaj-art-e4fe80c3db1b4bbd91fa1f3f32ca75f22025-08-20T03:09:09ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2025-04-011610.3389/fmicb.2025.15656311565631Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, ChinaYi Shi0Yi Shi1Yuguo Liu2Shen Li3Songwen Wu4Guozhu Ma5Yang Luan6Junjun Zhang7Yali Chen8Wanjing Liu9Tuo Shen10Caiqiao Wang11Jiru Xu12Department of Microbiology and Immunology, School of Medicine, Xi'an Jiaotong University, Xi'an, ChinaShaanxi Center for Disease Control and Prevention, Xi’an, ChinaDepartment of Rehabilitation Medicine, Zhujiang Hospital, Southern Medical University, Guangzhou, ChinaShaanxi Center for Disease Control and Prevention, Xi’an, ChinaDepartment of Public Health, Xi’an Medical University, Xi’an, ChinaShaanxi Center for Disease Control and Prevention, Xi’an, ChinaXi’an Center for Disease Control and Prevention, Xi’an, ChinaYanta Center for Disease Control and Prevention, Xi’an, ChinaHanzhong Center for Disease Control and Prevention, Hanzhong, ChinaAnkang Center for Disease Control and Prevention, Ankang, ChinaWeinan Center for Disease Control and Prevention, Weinan, China0Yulin Center for Disease Control and Prevention, Yulin, ChinaDepartment of Microbiology and Immunology, School of Medicine, Xi'an Jiaotong University, Xi'an, ChinaIntroductionMonophasic Salmonella Typhimurium, characterized by the absence of phase II flagellar antigens, has become increasingly prevalent as a foodborne pathogen, raising significant public health concerns due to its multidrug resistance. This study investigated the genomic characteristics and antibiotic resistance profiles of the monophasic Salmonella Typhimurium strains isolated from patients and food sources in Shaanxi Province, China.MethodsA total of 58 strains were collected between 2020 and 2021, with 4 strains isolated from food and 54 from patients. Whole genome sequencing was performed to assess genomic features. Antimicrobial susceptibility was tested against 17 antimicrobial agents using the broth dilution method, while pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing were employed for genetic characterization and epidemiological analysis. Phylogenetic analysis was conducted using single nucleotide polymorphism clustering.Results and discussionOur results revealed that all the strains belonged to the ST34 and did not carry virulence genes on pSLT (NC_003277). There were 12 strains carrying the STM2757 gene. The isolates exhibited a considerable diversity in PFGE subtypes. Phenotypic antimicrobial resistance showed that the strains were most resistant to tetracycline (94.34%; 50/53) and ampicillin (94.34%; 50/53), followed by streptomycin (88.68%; 47/53) and ampicillin/sulbactam (64.15%; 34/53). Resistance gene prediction highlighted the presence of 64 distinct genes, with aac(6’)-Iaa found in all strains (100%) and tet(B) in 93.1% of strains. Notably, the floR gene, relevant for resistance to phenicols, was observed in 44.83% of isolates. Genomic analysis revealed that 96.55% of strains were positive for the sodC1 virulence gene, whereas only 10.34% carried the sopE gene. The most plasmid replicon was IncQ1 (84.48%; 49/58), followed by IncHI2 (32.76%; 19/58) and IncHI2A (32.76%; 19/58). Single nucleotide polymorphism analysis showed that 2 strains were clustered together with SRR17830210 (UK outbreak isolate) with a bootstrap value of 0.949. There were only 12 allelic differences between SNXiAn21SAL011 and the reference strain. Conclusively, the monophasic Salmonella Typhimurium ST34 strains in Shaanxi Province demonstrated unique genomic and antimicrobial resistance traits. This study may help to prevent outbreaks and rationalize salmonellosis antimicrobial therapeutics.https://www.frontiersin.org/articles/10.3389/fmicb.2025.1565631/fullsalmonellaantimicrobial resistancevirulence factorsplasmid repliconsWGSSNP
spellingShingle Yi Shi
Yi Shi
Yuguo Liu
Shen Li
Songwen Wu
Guozhu Ma
Yang Luan
Junjun Zhang
Yali Chen
Wanjing Liu
Tuo Shen
Caiqiao Wang
Jiru Xu
Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China
Frontiers in Microbiology
salmonella
antimicrobial resistance
virulence factors
plasmid replicons
WGS
SNP
title Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China
title_full Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China
title_fullStr Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China
title_full_unstemmed Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China
title_short Genomic characteristics and antibiotic resistance profiles of monophasic Salmonella Typhimurium in Shaanxi Province, China
title_sort genomic characteristics and antibiotic resistance profiles of monophasic salmonella typhimurium in shaanxi province china
topic salmonella
antimicrobial resistance
virulence factors
plasmid replicons
WGS
SNP
url https://www.frontiersin.org/articles/10.3389/fmicb.2025.1565631/full
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