Plasmid-Encoded bla_NDM-5 Gene That Confers High-Level Carbapenem Resistance in Salmonella Typhimurium of Pork Origin

Abstract

Purpose

Carbapenem resistance is rarely reported in Salmonella Typhimurium, especially from a food origin. Here, we report a plasmid-mediated mobile carbapenem-resistant bla_NDM-5 gene in Salmonella Typhimurium isolated from pork in Shanghai, China in 2016.

Patients and Methods

In July 2016, the S. Typhimurium SH160 strain was recovered from minced pork meat purchased from a supermarket in Yangpu District, Shanghai, China. Antimicrobial susceptibility testing, multi-locus sequence typing, conjugation, S1-PFGE, southern hybridization, whole-genome sequencing and data analysis were performed.

Results

This isolate was found to be a ST34 strain and resistant to carbapenems, cephalosporins, and most other commonly used antibiotics. The bla_NDM-5 gene was harbored by a 46161-bp IncX3 plasmid which was found to be transferable. The IncX3 plasmid contains a composite cassette, consisting of ISSwil-IS3000-ΔISAba125-IS5-bla_NDM-5-bleMBL-trpF-dsbC-IS26-ctuA1-ΔumuD. In addition, this strain was found to harbor an additional 161706-bp IncHI2 plasmid which carries nine resistant genes, such as aadA1, aadA3, aph(3ʹ)-la, sul1, sul2, sul3, floR, cmlA and dfrA12.

Conclusion

We reported the S. Typhimurium with transferable IncX3 plasmid harboring bla_NDM-5 gene from minced pork. We characterized the complete genetic features of the plasmid, which demonstrated the potential for spreading in different bacterial pathogens. Therefore, extensive surveillance and monitoring for carbapenem-resistant bacterium in the food chain and public health are urgently required.

Keywords:

• S. Typhimurium
• pork
• bla_NDM-5
• public health

Acknowledgments

This research was supported by the National Key R&D Program of China (2017YFC1600101, 2018YFD0500500); National Natural Science Foundation of China (31972762); Pearl River S&T Nova Program of Guangzhou (201806010183); Province Science and Technology of Guangdong Research Project (2017A020208055); Guangdong Key S&T Program (Grant no. 2019B020217002) from the Department of Science and Technology of Guangdong Province; Walmart Foundation (SA1703162); National Broiler Industry Technology System Project (cARS-41-G16).

Disclosure

The authors report no conflicts of interest in this work.