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

PURPOSE: Carbapenem resistance is rarely reported in Salmonella Typhimurium, especially from a food origin. Here, we report a plasmid-mediated mobile carbapenem-resistant blaNDM-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 blaNDM-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-blaNDM-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(3')-la, sul1, sul2, sul3, floR, cmlA and dfrA12.

CONCLUSION

We reported the S. Typhimurium with transferable IncX3 plasmid harboring blaNDM-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.