title: [Distribution of drug inactive enzyme genes in bacterial isolates and mechanism of its induction and inhibition].
abstract: OBJECTIVE
  To determine the distribution and the predominant gene carrying model of drug inactive enzyme genes in bacterial isolates, and the mechanism of its induction and inhibition.
  
  
  METHODS
  The β-lactam, aminoglycosides and macrolides inactive enzyme genes were detected by PCR and sequencing in S. aureus, E.coli, K. pneumoniae, A. baumannii and E. cloacae isolates. The expression of inactive enzyme genes were examined by real-time fluorescent quantitative RT-PCR when the bacterial isolates were treated with antibiotics or a histidine kinase blocker closantel.
  
  
  RESULTS
  In 63 isolates of E.coli, 4 kinds of β-lactam, 2 aminoglycosides and 1 macrolides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were [TEM+CTX-M]+aac(3)-II+mphA (25.4 %) and [TEM+CTX-M]+ aac (6')-I b (20.6%). In 24 isolates of S.aureus, 2 kinds of β-lactam and 3 aminoglycosides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were aph (3')(41.7%) or aac (6)-I e-aph (2)-I a (25.0%). In 28 isolates of K.pneumoniae, 4 kinds of β-lactam and 2 aminoglycosides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were [TEM+SHV]+[aac(6')-I b+aac (3)-II](28.6 %) and [TEM+SHV]+[aac(6')-I b+aac (3)-II]+ mphA (17.8 %). The isolates of A.baumannii and E.cloacae also had a predominant model to carry 2 or 3 kinds of inactive enzyme-encoding genes. 1/4 MIC of penicillin, cefotaxime or streptomycin induced the up-regulation of expression of 3 β-lactam or 4 aminoglycosides inactive enzyme-encoding genes (P<0.05), and this effect was inhibited by closantel (P<0.05).
  
  
  CONCLUSIONS
  The bacterial isolates frequently carry multiple kinds of inactive enzyme-encoding genes with different predominant gene-carrying models.Low concentration antibiotics can induce the up-regulation of inactive enzyme gene expression, which can be inhibited by histidine kinase blocker.
authors.affiliation: Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou 310058, China.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Wu
authors.forename: Aihua
authors.initials: A
authors.lastname: Sun
authors.forename: Jinfang
authors.initials: J
authors.lastname: Zhao
authors.forename: Yumei
authors.initials: Y
authors.lastname: Ge
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D015854:Up-Regulation / Q000187:drug effects; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases