Characterization of plasmids in extensively drug-resistant acinetobacter strains isolated in India and Pakistan.

The blaNDM-1 gene is associated with extensive drug resistance in Gram-negative bacteria. This probably spread to Enterobacteriaceae from Acinetobacter spp., and we characterized plasmids associated with blaNDM-1 in Acinetobacter spp. to gain insight into their role in this dissemination. Four clinical NDM-1-producing Acinetobacter species strains from India and Pakistan were investigated. A plasmid harboring blaNDM-1, pNDM-40-1, was characterized by whole-genome sequencing of Acinetobacter bereziniae CHI-40-1 and comparison with related plasmids. The presence of similar plasmids in strains from Pakistan was sought by PCR and sequencing of amplicons. Conjugation frequency was tested and stability of pNDM-40-1 investigated by real-time PCR of isolates passaged with and without antimicrobial selection pressure. A. bereziniae and Acinetobacter haemolyticus strains contained plasmids similar to the pNDM-BJ01-like plasmids identified in Acinetobacter spp. in China. The backbone of pNDM-40-1 was almost identical to that of pNDM-BJ01-like plasmids, but the transposon harboring blaNDM-1, Tn125, contained two short deletions. Escherichia coli and Acinetobacter pittii transconjugants were readily obtained. Transconjugants retained pNDM-40-1 after a 14-day passage experiment, although stability was greater with meropenem selection. Fragments of pNDM-BJ01-like plasmid backbones are found near blaNDM-1 in some genetic contexts from Enterobacteriaceae, suggesting that cross-genus transfer has occurred. pNDM-BJ01-like plasmids have been described in isolates originating from a wide geographical region in southern Asia. In vitro data on plasmid transfer and stability suggest that these plasmids could have contributed to the spread of blaNDM-1 into Enterobacteriaceae.

Jones LS ，Carvalho MJ ，Toleman MA ，White PL ，Connor TR ，Mushtaq A ，Weeks JL ，Kumarasamy KK ，Raven KE ，Török ME ，Peacock SJ ，Howe RA ，Walsh TR ... -  《-》

Dissemination of the bla(NDM-5) Gene via IncX3-Type Plasmid among Enterobacteriaceae in Children.

The continuous emergence of novel New Delhi metallo-β-lactamase-5 (NDM-5)-producing Enterobacteriaceae isolates is receiving more and more public attention. Twenty-two NDM-5-producing strains were identified from 146 carbapenemase-producing Enterobacteriaceae (CRE) strains isolated from pediatric patients between January and March 2017, indicating that the blaNDM-5 gene has spread to children. All 22 isolates, including 16 Klebsiella pneumoniae strains, four Klebsiella aerogenes strains, and two Escherichia coli strains, showed significantly high resistance to β-lactam antibiotics (except aztreonam) but remained susceptible to tigecycline and colistin. K. pneumoniae and K. aerogenes strains were respectively defined as homologous clonal isolates by pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing (MLST) results confirmed the genetic relatedness with all K. pneumoniae strains belonging to sequence type (ST) 48. Two E. coli isolates (ST617 and ST1236) were considered genetically unrelated. Twenty-two blaNDM-5 plasmids were positive for the IncX3 amplicon and showed almost identical profiles after digestion with HindIII and EcoRI. Four representative strains (K. pneumoniae K725, K. aerogenes CR33, E. coli Z214, and E. coli Z244) were selected for further study. Plasmids harboring blaNDM-5 showed strong stability in both clinical isolates and transconjugants, without apparent plasmid loss after 100 serial generations. S1-PFGE followed by Southern blot analysis demonstrated that the blaNDM-5 gene was located on an ∼46-kb plasmid. Plasmid sequences of pNDM-K725, pNDM-CR33, and pNDM-Z214 were almost identical but were slightly different from that of pNDM-Z244. Compared with pNDM-Z244, ΔISAba125 and partial copies of IS3000 were missing. The genetic backgrounds of the blaNDM-5 gene in four strains were slightly different from that of the typical pNDM_MGR194. This study comprehensively characterized the horizontal gene transfer of the blaNDM-5 gene among different Enterobacteriaceae isolates in pediatric patients, and the IncX3-type plasmid was responsible for the spread.IMPORTANCE The emergence of CRE strains resistant to multiple antibiotics is considered a substantial threat to human health. Therefore, all the efforts to provide a detailed molecular transmission mechanism of specific drug resistance can contribute positively to prevent the further spread of multidrug-resistant bacteria. Although the new superbug harboring blaNDM-5 has been reported in many countries, it was mostly identified among E. coli strains, and the gene transfer mechanism has not been fully recognized and studied. In this work, we identified 22 blaNDM-5-positive strains in different species of Enterobacteriaceae, including 16 Klebsiella pneumoniae strains, four Klebsiella aerogenes strains, and two Escherichia coli strains, which indicated the horizontal gene transfer of blaNDM-5 among Enterobacteriaceae strains in pediatric patients. Moreover, blaNDM-5 was located on a 46-kb IncX3 plasmid, which is possibly responsible for this widespread horizontal gene transfer. The different genetic contexts of the blaNDM-5 gene indicated some minor evolutions of the plasmid, based on the complete sequences of the blaNDM-5 plasmids. These findings are of great significance to understand the transmission mechanism of drug resistance genes, develop anti-infection treatment, and take effective infection control measures.

Tian D ，Wang B ，Zhang H ，Pan F ，Wang C ，Shi Y ，Sun Y ... -  《mSphere》

In Silico Characterization of bla(NDM)-Harboring Conjugative Plasmids in Acinetobacter Species.

Tang B ，Wang C ，Sun D ，Lin H ，Ma J ，Guo H ，Yang H ，Li X ... -  《Microbiology Spectrum》

Co-Occurrence of Two Plasmids Encoding Transferable bla(NDM-1) and tet(Y) Genes in Carbapenem-Resistant Acinetobacter bereziniae.

Opazo-Capurro A ，Xanthopoulou K ，Arazo Del Pino R ，González-Muñoz P ，Matus-Köhler M ，Amsteins-Romero L ，Jerez-Olate C ，Hormazábal JC ，Vera R ，Aguilera F ，Fuller S ，Higgins PG ，González-Rocha G ... -  《Genes》

Novel plasmid and its variant harboring both a bla(NDM-1) gene and type IV secretion system in clinical isolates of Acinetobacter lwoffii.

Hu H ，Hu Y ，Pan Y ，Liang H ，Wang H ，Wang X ，Hao Q ，Yang X ，Yang X ，Xiao X ，Luan C ，Yang Y ，Cui Y ，Yang R ，Gao GF ，Song Y ，Zhu B ... -  《-》