江苏地区旺兹沃思沙门菌耐药和毒力基因及同源进化分析

Antimicrobial resistance, virulence genes, and evolution of Salmonella Wandsworth isolates from Jiangsu

摘要:

目的 针对分离自江苏地区4个不同奶牛场的粪便和垫料样本中的旺兹沃思沙门菌进行耐药表型和基因组特征分析。方法 采用玻片凝集法复核血清型，K-B纸片扩散法检测耐药性；利用全基因组测序(whole-genome sequencing, WGS)结合生物信息学分析多位点序列分型(multilocus sequence typing, MLST)类型、耐药基因和毒力基因特征，基于核心基因组单核苷酸多态性(single nucleotide polymorphism, SNPs)数据构建系统发育树，分析分离株间的同源性及不同来源流行菌株间的进化关系。结果 7株分离株鉴定为旺兹沃思沙门菌，药敏试验结果显示其对14种抗生素均敏感。MLST均为ST1498，携带1个氨基糖苷类药物耐药基因aac(6')-Iaa和8类106个毒力基因。SNPs分析表明，有6株分离株的同源性较高，其中3株分离株的SNPs差异为0。结论 本研究从江苏省奶牛场中分离出罕见的ST1498型旺兹沃思沙门菌，该菌对测试的抗菌药物均未显示耐药性，携带1种耐药基因和多种毒力基因。发现同一奶牛场存在旺兹沃思沙门菌的克隆传播现象，提示应加强奶牛场中沙门菌的监测，以减轻潜在的流行病学风险。

Abstract:

Objective To investigate the antimicrobial resistance phenotypes and genomic characteristics of Salmonella Wandsworth isolates from fecal and bedding samples across four dairy farms in Jiangsu.Methods Serotyping was reconfirmed by the slide agglutination method, and antimicrobial susceptibility was determined via the Kirby-Bauer disk diffusion assay. Whole-genome sequencing was performed, followed by bioinformatics analysis to characterize multilocus sequence typing (MLST) profiles, antimicrobial resistance genes, and virulence genes. A phylogenetic tree was built based on core genome single nucleotide polymorphisms (SNPs) to assess genetic homology among strains and elucidate population evolutionary relationships between prevalent strains from diverse sources.Results Seven Salmonella Wandsworth isolates were identified, all exhibiting susceptibility to 14 tested antimicrobials. The isolates were identified as ST1498 by MLST, harboring the aminoglycoside resistance gene aac(6')-Iaa and 106 virulence genes spanning eight functional categories. The analysis of SNPs revealed high genetic homogeneity, with six isolates clustering closely and three isolates showing a difference of zero in SNPs.Conclusion This study isolated a rare ST1498-type Salmonella Wandsworth from dairy farms in Jiangsu. The isolates demonstrate susceptibility to all tested antimicrobials while harboring a resistance gene and multiple virulence genes. These findings highlight the necessity of enhanced Salmonella surveillance in dairy farms to mitigate potential epidemiological risks.