Molecular characteristics of clinical IMP-producing Klebsiella pneumoniae isolates: novel IMP-90 and integron In2147.

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.

In vitro Antimicrobial Activity and Dose Optimization of Eravacycline and Other Tetracycline Derivatives Against Levofloxacin-Non-Susceptible and/or Trimethoprim-Sulfamethoxazole-Resistant Stenotrophomonas maltophilia.

Purpose: To better guide clinical use, we determined the in vitro antimicrobial activity of the new drug eravacycline and other tetracycline derivatives against levofloxacin (LVFX)-non-susceptible and/or trimethoprim-sulfamethoxazole (TMP-SMZ)-resistant Stenotrophomonas maltophilia and evaluated their dosing regimens. Methods: Seventy-seven unique strains of S. maltophilia were isolated from sputa samples and airway aspirate samples that were either LVFX-non-susceptible and/or TMP-SMZ-resistant. Monte Carlo simulations were performed for different dosing regimens according to the population pharmacokinetic parameters of antibiotics in patients with respiratory tract infections at the minimum inhibitory concentration (MIC). Results: Eravacycline had excellent in vitro antibacterial activity against LVFX-non-susceptible and/or TMP-SMZ-resistant S. maltophilia. Monte Carlo simulations showed that for LVFX-non-susceptible strains, the cumulative fraction of response (CFR) of minocycline at the conventional recommended dose of 100 mg q12 h was 90.90%; for TMP-SMZ-resistant strains, the CFR of minocycline at a high dose of 200 mg q12 h was only 91.64%. For strains resistant to both LVFX and TMP-SMZ, the CFR of minocycline at a high dose of 200 mg q12 h was 89.81%. In contrast, the CFR of tigecycline was less than 40%, even at a dose of 100 mg q12 h. Conclusion: For pneumonia, minocycline is better for S. maltophilia that is non-susceptible to LVFX; for TMP-SMZ-resistant strains and strains that are not susceptible to either LVFX or TMP-SMZ, the efficiency of eravacycline requires further evaluation. Eravacycline may be a better choice for extremely resistant S. maltophilia strains that are non-susceptible to LVFX, TMP-SMZ, and minocycline.

Molecular analysis of clinical Citrobacter spp. isolates: Acquisition of the Yersinia high-pathogenicity island mediated by ICEkp in C. freundii.

Background: Studies on Citrobacter spp. are limited, hindering our understanding of its species evolution and medical relevance. Methods: A 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. Results: A 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. Conclusion: Conventional 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.

Complexes of ionic liquids with poly(ethylene glycol)s.

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.

Erratum: (4R)-Ethyl 4-(4-chloro-phen-yl)-2-hydr-oxy-5-oxo-2,3,4,5-tetra-hydro-pyrano[3,2-c]chromene-2-carboxyl-ate. Corrigendum.

The absolute configuration in the title of the paper by Wang, Zhang, Xu & Zhang [Acta Cryst. (2010), E66, o217] is corrected.[This corrects the article DOI: 10.1107/S1600536809051976.].

Ethyl (2S,4R)-4-(4-bromo-phen-yl)-2-hydr-oxy-5,10-dioxo-3,4,5,10-tetra-hydro-2H-benzo[g]chromene-2-carboxyl-ate.

In the crystal structure of the title compound, C(22)H(17)BrO(6), the quinone ring makes a dihedral angle of 81.84 (3)° with the benzene ring. The chiral C atoms, viz. the ring C atoms bearing the hydr-oxy and bromo-phenyl substituents, exhibit R and S configurations, respectively. The terminal ethyl group of the -CO(2)CH(2)CH(3) group is disordered over two sets of sites with site-occupancy factors of 0.64 (1) and 0.36 (1). Inter-molecular O-H⋯O inter-actions further stabilize the crystal packing.

(4R)-Ethyl 4-(4-chloro-phen-yl)-2-hydr-oxy-5-oxo-2,3,4,5-tetra-hydro-pyrano[3,2-c]chromene-2-carboxyl-ate.

The title compound, C(21)H(17)ClO(6), is optically pure and adopts an R configuration. It was obtained by an organocatalytic asymmetric Michael addition of 4-hydroxy-coumarin with (E)-ethyl 4-(4-chloro-phen-yl)-2-oxobut-3-enoate. The structure consists of a tetra-hydro-pyran unit fused to the coumarin ring ring system. The hydroxyl and phenyl groups are on the same side of the tetra-hydro-pyrane ring. The benzene ring is almost perpendicular to the coumarin ring [dihedral angle of 72.89 (3)°]. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds are observed. An intra-molecular O-H⋯O contact also occurs.

(2R,5S)-5-Benzyl-2,3-dimethyl-4-oxo-2-phenyl-imidazolidin-1-ium chloride.

The title hydro-chloride salt, C(18)H(21)N(2)O(+)·Cl(-), is an imidazolidinone catalyst, which was derived from L-phenyl-alanine through cyclization with acetophenone. The imidazolidinone compound has a five-membered heterocyclic ring including two chiral centres. The imidazolidinone ring displays an envelope conformation, with the flap protonated N atom lying 0.497 (3) Šabove the mean plane of the remaining four atoms. In the crystal structure, one-dimensional supra-molecular chains parallel to the crystallographic 2(1) screw axis are formed by N-H⋯Cl hydrogen bonds involving the NH(2) (+) and Cl(-) groups. Intra-molecular N-H⋯Cl inter-actions are also present.

Ethyl 2-hydr-oxy-5-oxo-4-phenyl-2,3,4,5-tetra-hydro-pyrano[3,2-c]chromene-2-carboxyl-ate.

The main structural unit of the title compoud, C(21)H(18)O(6), is a fused three-ring group consisting of coumarin and tetra-hydro-pyrane ring systems. Two C atoms of the tetra-hydro-pyran ring are displaced by 0.295 (3) and -0.360 (2) Šfrom the mean plane of coumarin ring. The dihedral angle between the phenyl and coumarin rings is 73.94 (3)°. Inter-molecular O-H⋯O hydrogen bonds are present in the crystal structure.

(2R,4R)-2-Hydr-oxy-4-(2-methoxy-phen-yl)bicyclo-[3.3.1]nonan-9-one.

The title compound, C(16)H(20)O(3), contains a bicyclic ring system with two chiral centers. The crystal structure is stabilized by inter-molecular O-H⋯O hydrogen bonds. The absolute configuration was established by the stereo-selectivity of the asymmetric organocatalysis.