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Purpose: The isolation rate of extended spectrum ß-lactamase (ESBL)-producing Escherichia coli is increasing, posing a challenge to clinical anti-infective therapy. This study aims to provide new insight into the genomic characteristics and antimicrobial resistance mechanisms of extended spectrum ß-lactamase producing E. coli isolates recovered from a district hospital in China. Methods: A total of 36 ESBL-producing E. coli isolates were collected from body fluid samples from a Chinese district hospital. All isolates were subjected to whole genome sequencing to identify their antimicrobial resistance genes, virulence genes, serotypes, sequence types, and phylogenetic relationships by BacWGSTdb 2.0 webserver. Results: Among these isolates, all were resistant to cefazolin, cefotaxime, ceftriaxone, ampicillin, 24 (66.7%) were resistant to aztreonam, 16 (44.4%) were resistant to cefepime, and 15 were resistant (41.7%) to ceftazidime. The blaCTX-M gene was detected in all ESBL-producing E. coli isolates. Two isolates carrying two different types of blaCTX-M genes simultaneously. The carbapenem resistance gene blaKPC-2 was detected in one (2.8%) isolate. A total of 17 sequence types (STs) were found, with ST131 accounting for the majority (n =13; 36.1%). The most common serotype was O16:H5 associated with seven ST131 strains, followed by O25:H4/ST131 (n = 5) and O75:H5/ST1193 (n = 5). Evaluation of clonal relatedness revealed that all blaCTX-M gene-carrying E. coli had a difference of SNPs range from 7 to 79,198, which could be divided into four clusters. Only 7 SNPs could be found between EC266 and EC622, indicating that they are variants of the same clonal lineage. Conclusion: This study investigated the genomic characteristics of ESBL-producing E. coli isolates recovered from a district hospital in China. Continuous surveillance of ESBL-producing E. coli infections is imperative to create efficient strategies for controlling the transmission of these multi-drug resistant bacteria in clinical and community settings.
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Background: The transmission of carbapenem-resistant Enterobacterales pose a significant threat to global public health, which weakens the effectiveness of most antimicrobial agents. The aim of this study is to present the genomic characteristics of a multidrug-resistant Escherichia coli, which contains both blaKPC-2 and blaCTX-M-15 genes, discovered from a respiratory infection in China. Methods: The antimicrobial susceptibility of E. coli isolate 488 was measured by using the broth microdilution method. The Oxford Nanopore MinION and Illumina NovaSeq 6000 platforms were applied to determine the whole-genome sequence of this isolate. De novo assembly of short Illumina reads and long MinION reads were performed by Unicycler. In silico multilocus sequence typing (MLST), antimicrobial resistance genes and plasmid replicon types were determined using the genome sequencing data. Additionally, a pairwise core genome single nucleotide polymorphism (cgSNP) comparison between E. coli 488 and all ST648 E. coli strains retrieved from NCBI GenBank database were conducted using the BacWGSTdb 2.0 server. Results: E. coli 488 was resistant to aztreonam, levofloxacin, cefepime, fosfomycin, amikacin, imipenem, cefotaxime, and meropenem. The complete genome sequence of E. coli 488 (belong to ST648) is made up of eleven contigs totaling 5,573,915 bp, including one chromosome and ten plasmids. Eight antimicrobial resistance genes were identified, including blaKPC-2 located in a 46,161 bp IncI1-type plasmid and the blaCTX-M-15 gene situated in the chromosome. Other two E. coli S617-2 and R616-1 isolates, recovered from China in 2018, are the closest relatives of E. coli 488, with only 52 SNPs difference. The genome also contains at least 57 genomic islands and several IS elements. Conclusion: Our study reveals the first ST648 E. coli isolate containing both blaKPC-2 and blaCTX-M-15 in China. These results could provide valuable insights into the genetic characteristics, antimicrobial resistance mechanisms, and transmission dynamics of carbapenem-resistant Enterobacterales in clinical settings.
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Polyvinyl alcohol (PVA)/carboxyl methyl cellulose sodium (CMC)/Na2CO3 composite films with different contents of Na2CO3 were prepared by blending and solution-casting. The effect of Na2CO3 on the microstructure of PVA/CMC composite film was analyzed by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). Its macroscopic properties were analyzed by water sorption, solubility, and dielectric constant tests. The results show that the microstructure of PVA/CMC/Na2CO3 composite films was different from that of PVA and PVA/CMC composite films. In addition, compared to PVA and PVA/CMC composite films, the water sorption of PVA/CMC/Na2CO3 composite films relatively increased, the solubility in water significantly decreased, and the dielectric properties significantly improved. All these results indicate that the hydrogen bonding interaction between PVA and CMC increased and the crystallinity of PVA decreased after the addition of Na2CO3. This was also a direct factor leading to increased water sorption, decreased solubility, and enhanced dielectric properties. The reaction mechanism of PVA, CMC, and Na2CO3 is proposed to further evaluate the effect of Na2CO3 on the microstructure and macroscopic properties of PVA/CMC/Na2CO3 composite films.