The self-assembly behavior of ionic liquids with acyclic polyethers was studied. The cations of 1-alkyl-3-methylimidazolium salts and 1-alkylpyridinium salts could form complexes at a ratio of 1:1 with poly(ethylene glycol)-800 (PEG800) and poly(propylene glycol)-1000 (PPG1000) in which the chain length was suitable to wrap around the cations. On the basis of the investigation by NMR, mass spectrometry, UV-vis spectroscopy, and TG analysis, the formation and characteristics of the novel complexes were discussed.

A highly efficient organocatalytic synthesis of lapachol analogues from the Michael addition of naphthoquinone to various α,β‐unsaturated ketones catalyzed by primary amines is presented. Good to high yields (up to 93 %) and high to excellent enantioselectivities (up to 98 % ee) were obtained for the target compounds. MS (ESI) provided evidence for the key intermediates in the proposed mechanism.

Background Since the first report of carbapenem-resistant Klebsiella pneumoniae isolates in China in 2007, the prevalence of CRKP and CRE has increased significantly. However, the molecular characteristics of IMP-producing Klebsiella pneumoniae (IMPKp) are rarely reported. Methods A total of 29 IMPKp isolates were collected from a Chinese tertiary hospital from 2011 to 2017. Clinical IMPKp were identified by VITEK®MS, and further analyzed by whole-genome DNA sequencing with HiSeq and PacBio RSII sequencer. Sequencing data were analyzed using CSI Phylogeny 1.4, Resfinder, PlasmidFinder and the MLST tool provided by the Centre for Genomic Epidemiology. The analysis results were visualized using iTOL editor v1_1. The open reading frames and pseudogenes were predicted using RAST 2.0 combined with BLASTP/BLASTN searches against the RefSeq database. The databases CARD, ResFinder, ISfinder, and INTEGRALL were performed for annotation of the resistance genes, mobile elements, and other features. The types of blaIMP in clinical isolates were determined by BIGSdb-Pasteur. Integrons were drawn by Snapgene, and the gene organization diagrams were drawn by Inkscape 0.48.1. Results Four novel ST type, including ST5422, ST5423, ST5426 and ST5427 were identified. The IMP-4 and IMP-1 were the dominant IMP type. The majority of blaIMP-carrying plasmids belonged to IncN and IncHI5. Two novel blaIMP-carrying integrons (In2146 and In2147) were uncovered. A novel variant blaIMP-90 presented in novel integron In2147 has been identified. Conclusions IMPKp showed low prevalence in China. Novel molecular characteristics of IMPKp have been identified. Continuous monitoring of IMPKp shall also be carried out in the future.

BackgroundStudies on Citrobacter spp. are limited, hindering our understanding of its species evolution and medical relevance.MethodsA total of 164 clinical Citrobacter spp. isolates were collected from 2017 to 2020 and identified by VITEK MALDI-TOF MS or VITEK-2 Gram-Negative Identification Card. All isolates were further analyzed by whole-genome sequencing using a HiSeq sequencer. All sequences were processed using different modules of the PGCGAP integrated package: Prokka and fastANI were used for annotation and average nucleotide identification (ANI), respectively. Antibiotic resistance and virulence genes were identified by searching CARD, ResFinder, and VFDB databases, respectively. Strains were identified using Ribosomal Multi-locus Sequence Typing (rMLST) classification based on 53 ribosome protein subunits (rps). The evolutionary relationship was analyzed using kSNP3 and visualized by iTOL editor v1_1. Genetic environments were compared by BLAST and visualized by Easyfig 2.2.5. The pathogenicity of some Citrobacter freundii isolates was confirmed by Galleria mellonella larvae infection test.ResultsA total of 14 species of Citrobacter spp. were identified from 164 isolates. However, 27 and 11 isolates were incorrectly identified as C. freundii and Citrobacter braakii by MALDI-TOF MS, respectively. In addition, MS also failed to identify Citrobacter portucalensis. The virulence genes mainly encoded proteins related to flagella and iron uptake systems. Citrobacter koseri isolates (n = 28) contained two iron uptake systems, coding yersiniabactin and aerobactin, respectively. C. braakii isolates (n = 32), like Salmonella, carried Vi capsule polysaccharide synthesis genes. The yersiniabactin gene clusters identified in five C. freundii isolates are located on various ICEkp elements and have not been reported previously. Moreover, ICEkp-carrying C. freundii showed diverse pathogenic features.ConclusionConventional methods have significant defects in identifying Citrobacter spp. ICEkp-like elements-mediated acquirement of the Yersinia high-pathogenicity island was identified for the first time in C. freundii.

[Acta Cryst. (2010), E66, o217] is corrected.In the paper by Wang et al. (2010), the chemical name given in the Title should be '(2R,4R)-Ethyl 4-(4-chlorophenyl)-2-hydroxy-5-oxo-2,3,4,5-tetrahydropyrano[3,2-c]chromene-2-carboxylate'. The absolute configuration was established by anomalous-dispersion effects in diffraction measurements on the crystal. The revised scheme is shown below.