Shi Yi, Liu Yuguo, Li Shen, Wu Songwen, Ma Guozhu, Luan Yang, Zhang Junjun, Chen Yali, Liu Wanjing, Shen Tuo, Wang Caiqiao, Xu Jiru
Department of Microbiology and Immunology, School of Medicine, Xi'an Jiaotong University, Xi'an, China.
Shaanxi Center for Disease Control and Prevention, Xi'an, China.
Front Microbiol. 2025 Apr 11;16:1565631. doi: 10.3389/fmicb.2025.1565631. eCollection 2025.
Monophasic 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 Typhimurium strains isolated from patients and food sources in Shaanxi Province, China.
A 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.
Our 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 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 found in all strains (100%) and (B) in 93.1% of strains. Notably, the 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 virulence gene, whereas only 10.34% carried the 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 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.
单相鼠伤寒沙门氏菌的特征是缺乏II期鞭毛抗原，作为一种食源性病原体，其流行程度日益增加，因其多重耐药性引起了重大的公共卫生关注。本研究调查了从中国陕西省患者和食物来源分离的单相鼠伤寒沙门氏菌菌株的基因组特征和抗生素耐药谱。
2020年至2021年共收集了58株菌株，其中4株从食物中分离，54株从患者中分离。进行全基因组测序以评估基因组特征。使用肉汤稀释法对17种抗菌药物进行药敏试验，同时采用脉冲场凝胶电泳（PFGE）和多位点序列分型进行基因特征分析和流行病学分析。使用单核苷酸多态性聚类进行系统发育分析。
我们的结果显示，所有菌株均属于ST34，且在pSLT（NC_003277）上不携带毒力基因。有12株携带该基因。分离株在PFGE亚型中表现出相当大的多样性。表型抗菌耐药性表明，菌株对四环素（94.34%；50/53）和氨苄西林（94.34%；50/53）耐药性最强，其次是链霉素（88.68%；47/53）和氨苄西林/舒巴坦（64.15%；34/53）。耐药基因预测突出显示存在64个不同基因，所有菌株（100%）中均发现该基因，93.1%的菌株中发现（B）基因。值得注意的是，44.83%的分离株中观察到与对酚类耐药相关的基因。基因组分析显示，96.55%的菌株毒力基因呈阳性，而只有10.34%的菌株携带该基因。最常见的质粒复制子是IncQ1（84.48%；49/58），其次是IncHI2（32.76%；19/58）和IncHI2A（32.76%；19/58）。单核苷酸多态性分析显示，2株菌株与SRR17830210（英国暴发分离株）聚类在一起，自展值为0.949。SNXiAn21SAL011与参考菌株之间只有12个等位基因差异。总之，陕西省的单相鼠伤寒沙门氏菌ST34菌株表现出独特的基因组和抗菌耐药特征。本研究可能有助于预防暴发并使沙门氏菌病抗菌治疗合理化。
