title: [Predominant β-lactamase genotypes of Escherichia coli isolates and induction and inhibition mechanisms of β-lactamase gene expression].
abstract: OBJECTIVE
  To understand the predominant β-lactamase genotypes and their carrying modes of Escherichia coli isolates in Zhejiang province, and the effects of β-lactam antibiotics on inducing or histidine kinase inhibitor closantel (CLO) on inhibiting the expression of β-lactamase genes.
  
  
  METHODS
  Micro-dilution method and E-test were applied to measure the resistant rate and minimal inhibitory concentration (MIC) in E. coli isolates against β-lactam antibiotics. PCR and sequence analysis of PCR products were conducted to detect the β-lactamase genotypes and their carrying modes. Real-time fluorescent quantitative RT-PCR and β-lactamase confirmation test were performed to determine the influence of 1/4 MIC penicillin and cefotaxime, and CLO on the transcription and expression of β-lactamase genes in the resistant E. coli isolates.
  
  
  RESULTS
  Among the 462 E. coli strains isolated in Zhejiang, 285 (61.7%) were resistant to penicillin, ampicillin, cefoxitin, cefotaxim and ceftazidime. In the 285 resistant isolates, the detection rate of TEM or CTX-M β-lactamase gene (83.2% or 75.1%) was significantly higher than that of KPC, SHV or OXA β-lactamase gene (1.4%-10.2%) (P<0.01) and the carrying rate of two or more β-lactamase genes (68.8%) was also significantly higher than that of single β-lactamase gene (31.2%) (P<0.01), and 61.4% of the resistant isolates carried TEM+CTX-M genes (P<0.01). Except KPC gene, 1/4 MIC of cefotaxim and penicillin induced a rapid increase of TEM-mRNA, CTX-M-mRNA, SHV-mRNA or OXA-mRNA levels (P<0.01), but 50-500 µg/ml CLO inhibited these levels (P<0.01). After pre-treatment with 100 µg/ml CLO, 82.8%-85.6% of the resistant isolates became sensitive to β-lactam antibiotics (P<0.01), while the detection rate of β-lactamases was also decreased from 95.1% to 16.1% (P<0.01).
  
  
  CONCLUSIONS
  TEM and CTX-M are the predominant β-lactamase genotypes in E. coli isolates in Zhejiang and TEM+CTX-M is the predominant carrying mode of β-lactamase genes. Low concentrations of β-lactam antibiotics can up-regulate the expression levels of β-lactamase genes in E. coli through bacterial two-component signaling systems, but this effect can be inhibited by CLO, a histidine kinase inhibitor.
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Zhejiang Traditional Chinese Medicine University, Hangzhou 310006, China.
authors.forename: Panli
authors.initials: P
authors.lastname: Tan
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Zhejiang Traditional Chinese Medicine University, Hangzhou 310006, China.
authors.forename: Zhejiong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Zhejiang Medical College.
authors.forename: Aihua
authors.initials: A
authors.lastname: Sun
authors.affiliation: Department of Medical Microbiology and Parasitology, Medical School of Zhejiang University.
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Zhejiang Traditional Chinese Medicine University, Hangzhou 310006, China; Email: xinqiuzh@163.com.
authors.forename: Jinfang
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002681:China; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D015964:Gene Expression Regulation, Bacterial; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases