Plasmid analysis of NDM metallo-ß-lactamase-producing Enterobacterales isolated in Vietnam.

Carbapenem-resistant Enterobacterales (CRE) represent a serious threat to public health due to the lack of treatment and high mortality. The rate of antimicrobial resistance of Enterobacterales isolates to major antimicrobials, including carbapenems, is much higher in Vietnam than in Western countries, but the reasons remain unknown due to the lack of genomic epidemiology research. A previous study suggested that carbapenem resistance genes, such as the carbapenemase gene blaNDM, spread via plasmids among Enterobacterales in Vietnam. In this study, we characterized blaNDM-carrying plasmids in Enterobacterales isolated in Vietnam, and identified several possible cases of horizontal transfer of plasmids both within and among species of bacteria. Twenty-five carbapenem-nonsusceptible isolates from a medical institution in Hanoi were sequenced on Illumina short-read sequencers, and 13 blaNDM-positive isolates, including isolates of Klebsiella pneumoniae, Escherichia coli, Citrobacter freundii, Morganella morganii, and Proteus mirabilis, were further sequenced on an Oxford Nanopore Technologies long-read sequencer to obtain complete plasmid sequences. Almost identical 73 kb IncFII(pSE11)::IncN hybrid plasmids carrying blaNDM-1 were found in a P. mirabilis isolate and an M. morganii isolate. A 112 kb IncFII(pRSB107)::IncN hybrid plasmid carrying blaNDM-1 in an E. coli isolate had partially identical sequences with a 39 kb IncR plasmid carrying blaNDM-1 and an 88 kb IncFII(pHN7A8)::IncN hybrid plasmid in a C. freundii isolate. 148-149 kb IncFIA(Hl1)::IncA/C2 plasmids and 75-76 kb IncFII(Yp) plasmids, both carrying blaNDM-1 were shared among three sequence type 11 (ST11) isolates and three ST395 isolates of K. pneumoniae, respectively. Most of the plasmids co-carried genes conferring resistance to clinically relevant antimicrobials, including third-generation cephalosporins, aminoglycosides, and fluoroquinolones, in addition to blaNDM-1. These results provide insight into the genetic basis of CRE in Vietnam, and could help control nosocomial infections.

Determination of the capsular polysaccharide structure of the Klebsiella pneumoniae ST512 representative strain KPB-1 and assignments of the glycosyltransferases functions.

Klebsiella pneumoniae strain KPB-1 was isolated in early 2011 from the pleural fluid of an inpatient admitted at an Italian hospital. It was characterized to produce the KPC-3 carbapenemase and to belong to sequence type 512, a derivative of sequence type 258 clade II characterized by the cps-2 gene cluster. The K-antigen of K. pneumoniae KPB-1 was purified and its structure determined by using GLC-MS of appropriate carbohydrate derivatives and 1D and 2D NMR spectroscopy of the native polysaccharide. All the collected data demonstrated the following repeating unit for the K. pneumoniae KPB-1 capsular polysaccharide: The reactions catalysed by each glycosyltransferase in the cps-2 gene cluster were assigned on the basis of structural homology with other Klebsiella K antigens.