Antimicrobial resistance and genomic characteristics of Salmonella typhimurium and its monophasic variants in Hangzhou
10.3760/cma.j.cn112309-20231120-00139
- VernacularTitle:杭州地区鼠伤寒沙门菌及其单相变种耐药特征与基因组分析
- Author:
Zhibei ZHENG
1
;
Hua YU
1
;
Wei ZHENG
1
;
Pan ZHAO
1
;
Xiuqin LOU
1
;
Lingyi ZENG
1
;
Jingcao PAN
1
Author Information
1. 浙江省杭州市疾病预防控制中心卫生检验中心，杭州 310021
- Publication Type:Journal Article
- Keywords:
Salmonella typhimurium;
Monophasic variant of Salmonella typhimurium;
Multidrug resistance;
Whole-genome sequencing;
Multilocus sequence typing
- From:
Chinese Journal of Microbiology and Immunology
2024;44(12):1037-1047
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To analyze the antimicrobial resistance and genomic characteristics of Salmonella typhimurium and its monophasic variants isolated from human and food sources in Hangzhou. Methods:A total of 186 Salmonella typhimurium and its monophasic variants isolated in Hangzhou during the period from 2017 to 2021 were subjected to antimicrobial susceptibility testing and whole-genome sequencing, and the genomes from public databases were downloaded. Multilocus sequence typing and the identification of antimicrobial resistance (AMR) genes were performed using the sequencing data. Phylogenetic tree based on the single nucleotide polymorphism (SNP) sites in the genomes from Hangzhou and public databases was constructed. Results:The multidrug resistance (MDR) rate of the monophasic variant strains in Hangzhou was 95.4% (103/108). The MDR strains harbored ≥3 classes of AMR genes simultaneously and the most common resistance genotype was blaTEM-1B- tet( B)- sul2- aac(6′)- Ia (44.7%, 46/103). The MDR rate of Salmonella typhimurium strains was 75.6% (59/78), and 52.5% (31/59) of the MDR strains harbored ≥10 AMR genes simultaneously, with the most common resistance genotype being blaTEM-1B- qnrS1- tet( A)- tet( M)- cmlA1- floR- dfrA12- sul2- sul3- aac(6′)- Iaa (40.7%, 24/59). All of the 186 strains were positive for AMR gene aac (6 ′)- Iaa, and three monophasic variant strains which were resistant to polymyxin E was positive for mcr-1.1. ST19 accounted for 91.0% of the 78 Salmonella typhimurium strains (except for two strains belonging to ST34, two strains belonging to ST1544, and three strains untyped), and ST34 accounted for 96.3% of the 108 monophasic variant strains (except for four strains untyped). The phylogenetic tree showed that the ST19 strains dominated by serotype typhimurium and the ST34 strains dominated by monophasic variants were divided into two clades. In the ST19 clade, strains from Hangzhou were mainly clustered with the strains from other cities in Zhejiang Province as well as other provinces and cities in China, such as Jiangxi, Shanghai, and Shandong. Strains isolated from pig, duck, and chicken were the ones that were clustered with clinical strains. In the ST34 clade, most strains from Hangzhou were clustered together, and some strains were clustered with those isolated from other cities in Zhejiang Province as well as Beijing, Guangdong, Shanghai, etc. Strains isolated from pig and chicken were the ones that were clustered with clinical strains. Conclusions:The MDR rate of monophasic variant strains is higher than that of Salmonella typhimurium strains, and the latter is prominent by its harboring multiple AMR genes. The epidemic of Salmonella typhimurium and its monophasic variants in Hangzhou is mainly caused by the spread of ST19 and ST34 strains, respectively, and the clinical infection may be closely related to the consumption of pork and poultry meat. While transmitting locally, cross-region transmission of the two serovars in Zhejiang Province and cross-province transmission in China may also occur.
