title: Molecular characterization of CTX-Mβ-lactamases among Klebsiella pneumoniae isolated from patients at Tehran hospitals.
abstract: OBJECTIVE
  Plasmid-encoded CTX-M-group of extended-spectrum β-lactamases (ESBLs) represent a significant and rapidly emerging problem in most part of the world. The aim of the present study was to describe the prevalence of CTX-M producing Klebsiella pneumoniae at Tehran hospitals.
  
  
  METHODS
  Clinical isolates of K. pneumoniae (n=250) were collected from 10 hospitals of Tehran. Susceptibility to antimicrobial agents, MIC of cefotaxime and ESBLs production of collected isolates were detected. All ESBL-producing isolates were screened for bla CTX-M genes using PCR and DNA sequencing. Molecular typing of bla(CTX-M) harboring isolates was performed by Pulsed-field gel electrophoresis assay.
  
  
  RESULTS
  Of 250 K. pneumoniae clinical isolates, 102 isolates revealed ESBLs - phenotype. PCR assay and sequencing detected bla(CTX-M) genes in 71.5% (n= 73) of ESBL-producing isolates. The prevalence of CTX-M -I and CTX-M-III clusters among these isolates was 35.61% (n=26) and 21.9 % (n=16) respectively. Coexistence of CTX-M -I and CTX-M-III clusters was found among 42.5% (n= 31) of isolates. Of 102 isolates that were positive in the phenotypic confirmatory test (PCT), 29 isolates (28.4%) did not produce any amplicons in PCR for bla(CTX-M) gene. The results of PCR for CTX-M -II and CTX-M-IV clusters were also negative. Analysis of the 31 CTX-M producing K. pneumoniae isolates by PFGE typing showed 26 distinct patterns.
  
  
  CONCLUSIONS
  The bla CTX-M genes are widespread among Iranian isolates of K. pneumoniae. PFGE demonstrated the high diversity of K. pneumoniae harboring bla(CTX-M) in our study.
authors.affiliation: Department of Microbiology, Pasteur Institute, Tehran, Iran.
authors.forename: Shoeib
authors.initials: S
authors.lastname: Nematzadeh
authors.forename: N
authors.initials: N
authors.lastname: Shoeib
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Shahcheraghi
authors.forename: S
authors.initials: S
authors.lastname: Fereshteh
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Feizabadi
authors.forename: F M
authors.initials: FM
authors.lastname: Mehdi
authors.forename: Vajiheh Sadat
authors.initials: VS
authors.lastname: Nikbin
authors.forename: N V
authors.initials: NV
authors.lastname: Sadat
authors.forename: Leila
authors.initials: L
authors.lastname: Nasehi
authors.forename: N
authors.initials: N
authors.lastname: Leila
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D006761:Hospitals; D006801:Humans; D007492:Iran; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D010957:Plasmids / Q000032:analysis*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D001618:beta-Lactamases