Nematzadeh Shoeib, Shahcheraghi Fereshteh, Feizabadi Mohammad Mehdi, Nikbin Vajiheh Sadat, Nasehi Leila
Department of Microbiology, Pasteur Institute, Tehran, Iran.
Indian J Med Microbiol. 2011 Jul-Sep;29(3):254-7. doi: 10.4103/0255-0857.83908.
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.
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.
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.
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.
质粒编码的超广谱β-内酰胺酶（ESBLs）的CTX-M组在世界大部分地区是一个重大且迅速出现的问题。本研究的目的是描述德黑兰医院产CTX-M的肺炎克雷伯菌的流行情况。
从德黑兰的10家医院收集肺炎克雷伯菌临床分离株（n = 250）。检测收集的分离株对抗菌药物的敏感性、头孢噻肟的最低抑菌浓度（MIC）以及ESBLs的产生情况。使用聚合酶链反应（PCR）和DNA测序对所有产ESBLs的分离株进行bla CTX-M基因筛查。对携带bla(CTX-M)的分离株进行脉冲场凝胶电泳分析以进行分子分型。
在250株肺炎克雷伯菌临床分离株中，102株显示出ESBLs表型。PCR检测和测序在71.5%（n = 73）的产ESBLs分离株中检测到bla(CTX-M)基因。这些分离株中CTX-M -I和CTX-M-III簇的流行率分别为35.61%（n = 26）和21.9%（n = 16）。在42.5%（n = 31）的分离株中发现CTX-M -I和CTX-M-III簇共存。在102株表型确证试验（PCT）呈阳性的分离株中，29株（28.4%）在bla(CTX-M)基因的PCR中未产生任何扩增子。CTX-M -II和CTX-M-IV簇的PCR结果也为阴性。通过脉冲场凝胶电泳分型对31株产CTX-M的肺炎克雷伯菌分离株进行分析，显示出26种不同的模式。
bla CTX-M基因在伊朗肺炎克雷伯菌分离株中广泛存在。脉冲场凝胶电泳显示在我们的研究中携带bla(CTX-M)的肺炎克雷伯菌具有高度多样性。
