A Nationwide Plasmidome Surveillance in Thailand Reveals a Limited Variety of New Delhi Metallo-β-Lactamase-Producing Carbapenem-Resistant Clones and Spreading Plasmids.

Despite frequent identification of plasmids carrying carbapenemase genes, the transfer of plasmids carrying carbapenemase genes is not well recognized in clinical settings because of technical limitations. To investigate the detailed mechanisms of the spread of carbapenem-resistant (CRE), we performed multifaceted genomic surveillance of CRE isolates in Thailand and analyzed their plasmidome. We analyzed 371 isolates carrying and 114 isolates carrying obtained from clinical samples of 473 patients in 11 representative hospitals located in six provinces in Thailand between 2012 and 2017. The complete structures of plasmids carrying and chromosomal phylogeny were determined by combining Southern blotting hybridization analysis and our previously performed whole-genome short-read sequencing data. Dissemination of the gene among the isolates in Thailand was mainly owing to the nationwide clonal spread of Escherichia coli ST410 and regional clonal spreads of Escherichia coli ST361 and ST405. Analysis of -carrying isolates revealed nationwide dissemination of two specific plasmids and nationwide clonal dissemination of Klebsiella pneumoniae ST16 accompanied with regional disseminations of three distinctive K. pneumoniae clones (ST231, ST14, and ST147) with different plasmids. Dissemination of CRE carrying in Thailand is mainly based on nationwide clonal expansions of E. coli ST410 carrying and K. pneumoniae ST16 carrying , nationwide dissemination of two distinctive plasmids carrying , and accumulation of clonal expansions in regional areas. Although the overuse of antibiotics can promote CRE dissemination, the limited variety of transmitters highlights the importance of preventing horizontal dissemination among patients.