[Drug resistance and genomic characteristics of Salmonellaenterica serovar London from clinical and food sources in Hangzhou City from 2017 to 2021].

Objective: To analyze the drug resistance and genomic characteristics of Salmonella enterica serovar London isolated from clinical and food sources in Hangzhou City from 2017 to 2021. Methods: A total of 91 Salmonella enterica serovar London strains isolated from Hangzhou City from 2017 to 2021 were analyzed for drug susceptibility, pulsed field gel electrophoresis (PFGE) typing and whole genome sequencing. Multilocus sequence typing (MLST), core genome multilocus sequence typing (cgMLST) and detection of drug resistance genes were performed by using the sequencing data. Phylogenetic analysis was conducted to compare the 91 genomes from Hangzhou City with 347 genomes from public databases. Results: No significant difference in the drug resistance rate was observed between clinical strains and food strains to 18 drugs in Hangzhou City(all P>0.05), and the multidrug resistance (MDR) rate was 75.8% (69/91). Most strains were resistant to 7 drug classes simultaneously. One strain was resistant to Polymyxin E as well as positive for mcr-1.1, and 50.5% (46/91) of the strains were resistant to Azithromycin and were positive for mph(A). All 91 Salmonellaenterica serovar London strains were ST155, which were subdivided into 44 molecular types by PFGE and 82 types by cgMLST. Phylogenetic analysis showed that most strains from Hangzhou City (83/91) were clustered together, and a small number of human isolates from Europe, North America and pork isolates from Hubei and Shenzhen were mixed in the cluster. Other strains from Hangzhou City (8/91) were closely related to strains from Europe, America and Southeast Asia. Strains isolated from pork were the most closely related to clinical strains. Conclusion: The epidemic of Salmonella enterica serovar London in Hangzhou City is mainly caused by the spread of ST155 strains, which is mainly transmitted locally. At the same time, cross-region transmission to Europe, North America, Southeast Asia, and other provinces and cities in China may also occur. There is no significant difference in the drug resistance rate between clinical strains and food strains, and a high level of MDR is found in the strains. Clinical infection of Salmonella enterica serovar London may be closely related to pork consumption in Hangzhou City.目的： 分析2017—2021年杭州市临床和食品来源伦敦沙门菌的耐药与基因组特征。 方法： 对2017—2021年杭州市分离的91株伦敦沙门菌进行药敏分析、PFGE分型和全基因组测序；利用测序数据对菌株进行多位点序列分型（MLST）、核心基因组多位点序列分型（cgMLST）和耐药基因识别，并与公共数据库菌株比较进行系统发育分析。 结果： 临床株和食品株对18种药物的耐药率差异均无统计学意义（均P>0.05），其多重耐药率为75.8%（69/91），以同时耐7类药物的菌株居多，发现1株对多黏菌素E耐药且检出mcr-1.1基因的耐8类药物菌株；50.5%（46/91）的菌株对阿奇霉素耐药且检出mph（A）基因；91株伦敦沙门菌均为ST155型，分为44种PFGE带型和82种cgMLST型别；系统发育分析显示，大部分杭州菌株（83/91）自行聚集成簇，簇内混杂少量来自欧洲和北美洲的人分离株以及湖北、深圳等省市的猪肉分离株；少数杭州菌株（8/91）与分离自东南亚、欧洲、北美洲的菌株进化距离较近；与临床株距离较近的主要是猪肉分离株。 结论： 杭州市伦敦沙门菌的感染主要由ST155型菌株引起，以本地传播为主，同时与东南亚、欧洲、北美洲以及国内其他省市可能存在跨地传播；临床和食品来源菌株间耐药差异无显著意义，多重耐药现象较为普遍；其临床感染可能与猪肉消费密切相关。.