Genetic factors related to the widespread dissemination of ST11 extensively drug-resistant carbapenemase-producing Klebsiella pneumoniae strains within hospital / 中华医学杂志(英文版)

BACKGROUND@#Carbapenemase-producing Klebsiella pneumoniae (CP-Kp) poses distinct clinical challenges due to extensively drug resistant (XDR) phenotype, and sequence type (ST) 11 is the most dominant blaKPC-2-bearing CP-Kp clone in China. The purpose of this current retrospective study was to explore the genetic factors associated with the success of XDR CP-Kp ST11 strains circulated in the intensive care unit (ICU) of a Chinese tertiary hospital.@*METHODS@#Six ST11 XDR CP-Kp strains were identified between May and December 2014 and validated by minimum inhibitory concentration examination, polymerase chain reaction, and pyrosequencing. The six ST11 XDR CP-Kp, as well as three multi-drug resistant (MDR) and four susceptible strains, were sequenced using single-molecule real-time method. Comprehensively structural and functional analysis based on comparative genomics was performed to identify genomic characteristics of the XDR ST11 CP-Kp strains.@*RESULTS@#We found that ST11 XDR blaKPC-2-bearing CP-Kp strains isolated from inpatients spread in the ICU of the hospital. Functionally, genes associated with information storage and processing of the ST11 XDR CP-Kp strains were more abundant than those of MDR and susceptible strains, especially genes correlative with mobile genetic elements (MGEs) such as transposons and prophages. Structurally, eleven large-scale genetic regions taken for the unique genome in these ST11 XDR CP-Kp strains were identified as MGEs including transposons, integrons, prophages, genomic islands, and integrative and conjugative elements. Three of them were located on plasmids and eight on chromosomes; five of them were with antimicrobial resistance genes and eight with adaptation associated genes. Notably, a new blaKPC-2-bearing ΔΔTn1721-blaKPC-2 transposon, probably transposed and truncated from ΔTn1721-blaKPC-2 by IS903D and ISKpn8, was identified in all six ST11 XDR CP-Kp strains.@*CONCLUSION@#Our findings suggested that together with clonal spread, MGEs identified uniquely in the ST11 XDR CP-Kp strains might contribute to their formidable adaptability, which facilitated their widespread dissemination in hospital.

The effect of pre-freezing method on crystallinity of alanylglutamine / 中国药学杂志

OBJECTIVE: To research and regulate the crystal quality of alanylglutamine for improving their stability and pharmacodynamics as well as vacuum freeze-drying efficiency. METHODS: Scanning electron microscopy (SEM), X-ray powder diffractometer (XRD), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TG) as well as lyophilized experiments were used to investigate the effect of pre-freeze method on crystallinity and uniformity of particle size of alanylglutamine. RESULTS: The result of SEM revealed that the lyophilized alanylglutamine with accelerated pre-freeze method is small-size particle with low crystallinity. Then the lyophilized alanylglutamine with multi-step annealing pre-freeze method become uniformly large particle with high crystallinity. The RESULTS of XRD and DSC indicted that, comparing with the lyophilized alanylglutamine with accelerated pre-freeze method, the lyophilized sample with multi-step annealing pre-freeze method is easier to form the crystal medicine with uniform particle size, less crystal defects, high crystallinity. And the former has lower stability than the later. CONCLUSION: The final lyophilized experiment give us a CONCLUSION that using the multi-step annealing pre-freeze method can improve the freeze-drying efficiency and crystal quality of alanylglutamine, which to achieve the ultimate goal of cost and energy saving.