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A combined adsorption-discharge plasma catalytic process was used for the removal of NO(x) using zeolites as catalysts without external heating. It was found that the types of plasma carrier gases exert great effect on the conversion of adsorbed NO(x). The conversion of adsorbed NO(x) is much lower in N(2) plasma than in Ar plasma, which is attributed to the reverse reaction, NO(x) formation reaction. The momentary increase of oxygen species derived from the decomposition of adsorbed NO(x) is considered to be the main cause as their collisions with nitrogen species can generate NO(x) again. Thus, solid carbon was added to the catalyst to act as a scavenger for active oxygen species to improve the conversion of adsorbed NO(x) in N(2) plasma. A NO(x) removal rate of 97.8% was obtained on 8.5wt.% carbon mixed H-ZSM-5 at an energy efficiency of 0.758 mmol NO(x)/W·h.

Here, we report a multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-HvKP) strain of sequence type 23 (ST23) with a rare hybrid plasmid harboring virulence genes and blaCTX-M-24, and we analyze the genetic basis for relationship between genotypes and MDR-hypervirulence phenotypes. Further analysis indicates that the hybrid plasmid is formed by IS903D-mediated intermolecular transposition of the blaCTX-M-24 gene into the virulence plasmid. The emergence of MDR-HvKP strains, especially those carrying drug-resistant virulent plasmids, poses unprecedented threats/challenges to public health. This is a dangerous trend and should be closely monitored.

IncHI plasmids could be divided into five different subgroups IncHI1–5. In this study, the complete nucleotide sequences of seven blaIMP- or blaVIM-carrying IncHI5 plasmids from Klebsiella pneumoniae, K. quasipneumoniae, and K. variicola were determined and compared in detail with all the other four available sequenced IncHI5 plasmids. These plasmids carried conserved IncHI5 backbones composed of repHI5B and a repFIB-like gene (replication), parABC (partition), and tra1 (conjugal transfer). Integration of a number of accessory modules, through horizontal gene transfer, at various sites of IncHI5 backbones resulted in various deletions of surrounding backbone regions and thus considerable diversification of IncHI5 backbones. Among the accessory modules were three kinds of resistance accessory modules, namely Tn10 and two antibiotic resistance islands designated ARI-A and ARI-B. These two islands, inserted at two different fixed sites (one island was at one site and the other was at a different site) of IncHI5 backbones, were derived from the prototype Tn3-family transposons Tn1696 and Tn6535, respectively, and could be further discriminated as various intact transposons and transposon-like structures. The ARI-A or ARI-B islands from different IncHI5 plasmids carried distinct profiles of antimicrobial resistance markers and associated mobile elements, and complex events of transposition and homologous recombination accounted for assembly of these islands. The carbapenemase genes blaIMP-4, blaIMP-38 and blaVIM-1 were identified within various class 1 integrons from ARI-A or ARI-B of the seven plasmids sequenced in this study. Data presented here would provide a deeper insight into diversification and evolution history of IncHI5 plasmids.

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Objectives To dissect genomic features of IncpRBL16 plasmids from Pseudomonas. Methods An extensive genomic comparison was applied to all 17 available sequenced IncpRBL16 plasmids, including 8 sequenced in this study and another 2 sequenced in two of our previous studies. Results Conserved IncpRBL16 backbone markers repAIncpRBL16 together with its iterons, parB2–parA, che, pil and ter were present in all 17 plasmids. At least 18 regions or sites across IncpRBL16 genomes exhibited major modular differences, including insertion of accessory modules, deletion of backbone regions surrounding insertion sites and substitution of multiple-gene backbone regions. Ten plasmids carried a sole IncpRBL16 replicon, while exogenous acquisition of an auxiliary replicon (located in an accessory module) besides the primary IncpRBL16 replicon was observed in each of the remaining seven plasmids. The 17 IncpRBL16 plasmids carried at least 71 different accessory modules, notably including Tn1403-related regions, Tn7-family transposons, Tn6571-family transposons, integrative and conjugative elements, and integrative and mobilizable elements. There were a total of 40 known resistance genes, which were involved in resistance to 15 categories of antibiotics and heavy metals, notably including blaIMP-9, blaIMP-45, blaVIM-2, blaDIM-2, blaOXA-246, blaPER-1, aphA and armA. Conclusions Different IncpRBL16 plasmids contain different profiles of accessory modules and thus diverse collections of resistance genes. To the best of our knowledge, this is the first report of fully sequenced blaOXA-246-carrying (p12939-PER) and blaPER-1-carrying (p12939-PER and pA681-IMP) IncpRBL16 plasmids and also that of 14 novel (first identified in this study) and additionally 31 newly named (first designated in this study, but with previously determined sequences) mobile elements.

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