Salmonella Typhimurium with Eight Tandem Copies of blaNDM-1 on a HI2 Plasmid

Huijuan Song; Siyu Zou; Yi Huang; Cui Jian; Weiyong Liu; Lei Tian; Lu Gong; Zhongju Chen; Ziyong Sun; Yue Wang

doi:10.3390/microorganisms12010020

Salmonella Typhimurium with Eight Tandem Copies of bla_NDM-1 on a HI2 Plasmid

Microorganisms. 2023 Dec 22;12(1):20. doi: 10.3390/microorganisms12010020.

Authors

Huijuan Song¹, Siyu Zou¹, Yi Huang¹, Cui Jian¹, Weiyong Liu¹, Lei Tian¹, Lu Gong¹, Zhongju Chen¹, Ziyong Sun¹, Yue Wang¹

Affiliation

¹ Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.

Abstract

Carbapenem-resistant Salmonella has recently aroused increasing attention. In this study, a total of four sequence type 36 Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) isolates were consecutively isolated from an 11-month-old female patient with a gastrointestinal infection, of which one was sensitive to carbapenems and three were resistant to carbapenems. Via antibiotic susceptibility testing, a carbapenemases screening test, plasmid conjugation experiments, Illumina short-reads, and PacBio HiFi sequencing, we found that all four S. Typhimurium isolates contained a bla_CTX-M-14-positive IncI1 plasmid. One carbapenem-sensitive S. Typhimurium isolate then obtained an IncHI2 plasmid carrying bla_NDM-1 and an IncP plasmid without any resistance genes during the disease progression. The bla_NDM-1 gene was located on a new 30 kb multiple drug resistance region, which is flanked by IS26 and TnAs2, respectively. In addition, the ST_F0903R isolate contained eight tandem copies of the ISCR1 unit (ISCR1-dsbD-trpF-ble-bla_NDM-1-ISAba125Δ1), but an increase in MICs to carbapenems was not observed. Our work further provided evidence of the rapid spread and amplification of bla_NDM-1 through plasmid. Prompting the recognition of carbapenem-resistant Enterobacterales and the initiation of appropriate infection control measures are essential to avoid the spread of these organisms.

Keywords: IncHI2; NDM-1; PacBio HiFi sequencing; Salmonella Typhimurium; carbapenem resistance; tandem copies; whole-genome sequencing.

Grants and funding

This work was supported by grants from the National Science and Technology Basic Resources Survey Special Project (no. 2019FY101206 and no. 2019FY101200).