Purpose: 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.
Materials and 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.