Molecular Epidemiology and Antimicrobial Resistance Laboratory, Division of Epidemiology, Tel Aviv Medical Center, Tel Aviv, Israel.
J Antimicrob Chemother. 2010 Feb;65(2):243-8. doi: 10.1093/jac/dkp417. Epub 2009 Nov 24.
An extremely drug-resistant (XDR) clone of KPC-3-producing Klebsiella pneumoniae emerged in Israel in 2006, causing a nationwide outbreak. We aimed to characterize the local KPC-3-encoding plasmid carried by these isolates and study its contribution to antibiotic resistance.
Mechanisms of carbapenem resistance were investigated in seven selected isolates (isolated between 2006 and 2008) belonging to the epidemic clone. Isolates underwent MIC testing, and were examined for the presence of KPC, Tn4401, class I integron elements and additional antibiotic resistance genes. Plasmids were analysed by transformation, transconjugation, restriction mapping, curing and complementation experiments. Outer membrane protein (OMP) analysis was performed.
OMP analysis did not reveal loss of porins. KPC-3-producing K. pneumoniae isolates possessed various plasmids but all harboured a common self-transmissible 105 kb plasmid, termed pKpQIL, encoding bla(TEM-1) and bla(KPC-3). Curing of pKpQIL led to a complete loss of resistance to cephalosporins and carbapenems, proving its crucial role in carbapenem resistance. Transformation of plasmid pKpQIL into the cured Klebsiella strain resulted in full reconstitution of carbapenem resistance. The presence of all Tn4401 transposon elements located upstream of the KPC-3 gene was detected by PCR and sequencing. pKpQIL lacked additional antibiotic resistance genes.
Our findings demonstrate the presence of pKpQIL, a 105 kb KPC-3- and TEM-1-encoding plasmid, in the XDR K. pneumoniae epidemic strain in Israel. pKpQIL is unique and appears consistently in all isolates of this clone over the years. The extensive beta-lactam resistance phenotype of this clone is primarily mediated by this single self-transmissible plasmid.
产 KPC-3 肺炎克雷伯菌的极耐药（XDR）克隆于 2006 年在以色列出现，导致全国性爆发。我们旨在描述这些分离株携带的本地 KPC-3 编码质粒，并研究其对抗生素耐药性的贡献。
对属于流行克隆的 7 株选定分离株（2006 年至 2008 年期间分离）进行碳青霉烯类耐药机制的研究。进行分离株 MIC 检测，并检查 KPC、Tn4401、I 类整合子元件和其他抗生素耐药基因的存在情况。通过转化、转导、限制图谱分析、消除和互补实验分析质粒。进行外膜蛋白（OMP）分析。
OMP 分析未显示孔蛋白缺失。产 KPC-3 肺炎克雷伯菌分离株携带各种质粒，但均携带一种常见的可自主转移的 105 kb 质粒，称为 pKpQIL，编码 bla(TEM-1)和 bla(KPC-3)。pKpQIL 的消除导致对头孢菌素和碳青霉烯类药物的完全耐药性丧失，证明其在碳青霉烯类耐药性中起关键作用。质粒 pKpQIL 转化到已消除的克雷伯菌株中导致完全重建碳青霉烯类耐药性。通过 PCR 和测序检测到位于 KPC-3 基因上游的所有 Tn4401 转座子元件的存在。pKpQIL 缺乏其他抗生素耐药基因。
我们的研究结果表明，在以色列的 XDR 肺炎克雷伯菌流行株中存在 pKpQIL，这是一种 105 kb 的 KPC-3 和 TEM-1 编码质粒。pKpQIL 是独特的，多年来一直存在于该克隆的所有分离株中。该克隆的广泛β-内酰胺耐药表型主要由这单个自主转移质粒介导。
