Genomic insights into the emergence and spread of NDM-1-producing Vibrio spp. isolates in China

Background: Carbapenemase-producing Vibrio spp., which exhibit an XDR phenotype, have become increasingly prevalent and pose a severe threat to public health. Objectives: To investigate the genetic characteristics of NDM-1-producing Vibrio spp. isolates and the dissemination mechanisms of blaNDM-1 in Vibrio. Methods: A total of 1363 non-duplicate Vibrio spp. isolates collected from shrimp samples in China were subjected to antimicrobial susceptibility tests and screened for blaNDM-1. The blaNDM-1-positive isolates were further characterized by PFGE, MLST, conjugation and WGS using Illumina and Nanopore platforms. Plasmid stability and fitness cost were assessed using Escherichia coli J53, Klebsiella pneumoniae Kpt80 and Salmonella spp. SA2051 as recipient strains. Results: In total, 13 blaNDM-1-positive isolates were identified, all exhibiting MDR. WGS analysis revealed that the 13 blaNDM-1 genes were all associated with a derivative of Tn125. Plasmid analysis revealed that six blaNDM-1 genes were located in IncC plasmids and the other seven were carried by plasmids of two different novel types. Conjugation and plasmid stability assays showed that only the IncC plasmids could be transferred to all the recipient strains and could be stably maintained in the hosts. Conclusions: The emergence of the novel plasmids has contributed to the variable genetic contexts of blaNDM-1 in Vibrio spp. and IncC plasmids harbouring the blaNDM-1 gene could facilitate the spread of such genes between Vibrio spp. and other zoonotic pathogens, leading to a rapid dissemination of blaNDM-1 in bacterial pathogens worldwide.