Hui Li

Anhui Medical University, Luchow, Anhui Sheng, China

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Publications (3)3.69 Total impact

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    ABSTRACT: This study reports phenotypic and molecular characterization of a novel CTX-M beta-lactamase carried by two Klebsiella pneumoniae isolates collected from two hospitals in China. Conjugation experiment, Southern hybridization, susceptibility testing, isoelectric focusing, PCR, and sequencing techniques as well as clone, expression, purification and kinetics were carried out to describe the characterization of the novel CTX-M-type enzyme. The analyses of plasmid profiling and pulsed-field gel electrophoresis of the novel enzyme were performed to investigate epidemiology. The PCR products had 967 nucleotides and a novel CTX-M enzyme with a pI of 8.5 was implicated in this resistance: CTX-M-72. Two strains exhibited a clavulanic acid-inhibited substrate profile that included extended-spectrum cephalosporins. The amino acid sequence of the CTX-M-72 beta-lactamase differed from that of the CTX-M-3 beta-lactamase by the Arg-->Gly change at position 164. The novel enzyme was susceptible to ceftazidime, the same response being observed for other CTX-M enzymes. The substrates of the beta-lactamase were also characterized. Furthermore, two resistant genes of clinical strains were closely related. The emergence of a novel CTX-M-type extended-spectrum beta-lactamase was rarely described in other areas. This study illustrated the importance of molecular surveillance in tracking CTX-M-producing strains in large teaching hospitals, suggested the horizontal transfer of plasmid-borne bla(CTX-M) genes contributed to the dissemination of CTX-M enzymes in hospital environments, and emphasized the need for epidemiological monitoring.
    The Journal of General and Applied Microbiology 06/2009; 55(3):207-16. · 0.60 Impact Factor
  • The Journal of General and Applied Microbiology 01/2009; 55(3):207-216. DOI:10.2323/jgam.55.207 · 0.60 Impact Factor
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    ABSTRACT: The aim of the present study was to study the phenotypic and molecular characterization of 5 novel CTX-M-beta-1actamases carried by 5 Klebsiella pneumoniae isolates and 3 Escherichia coli isolates collected from 4 hospitals in Hefei, China. The purified PCR products were ligated with pGEM-Teasy vectors, expressed, and sequenced. The complete genes of the CTX-M-beta-lactamases were ligated with the pHSG398 vector to express prokaryotic recombinant proteins. Plasmids were extracted by rapid alkaline lysis protocol, and the PCR method was performed to determine whether the prokaryotic expression was successful or not. Antimicrobial susceptibility was tested and the phenotypes of transformants were determined according to criteria recommended by the Clinical and Laboratory Standards Institute. The kinetic parameters of enzymes were confirmed. The isoelectric points (pI) were determined by isoelectric focusing assay. Pulsed-field gel electrophoresis and plasmid profiling were performed. The PCR products had 1101 nucleotides and were determined as CTX-M-46, CTX-M-47, CTX-M-48, CTX-M-49, and CTX-M-50. All strains were resistant to cefotaxime, but most of them were susceptible or intermediate to ceftazidime. The phenotypes of novel enzymes were determined as extended-spectrum-beta-lactamases (ESBL). Penicillin G, cephalothin, cefuroxime, and cefotaxime were determined to good substrates, whereas ceftazidime hydrolysis was not detected. The pI of the 5 novel CTX-M-beta-lactamases were 8.0. CTX-M-derivatives could be the multiplex genesis in our area. This is the first report of these 5 novel plasmid-mediated CTX-M ESBL produced from China in the world. Molecular typing reveals notably different origin in genes encoding different CTX-M variants of 8 strains.
    Acta Pharmacologica Sinica 03/2008; 29(2):217-25. DOI:10.1111/j.1745-7254.2008.00736.x · 2.50 Impact Factor