IncFIIK plasmid harbouring an amplification of 16S rRNA methyltransferase-encoding gene rmtH associated to mobile element ISCR2. IncFIIk plasmid harbouring an amplification of 16S rRNA methyltransferase-encoding gene rmtH associated with mobile element ISCR2.

In this study, we report the complete sequence of a 114kb plasmid encoding the 16S rRNA methyltransferase-encoding gene rmtH. This plasmid was characterized in a carbapenemase-producing Klebsiella pneumoniae strain isolated in Lebanon. This is the first report of rmtH in a plasmid. The plasmid harbours an antibiotic resistance island associated to a novel composite transposon encoding the extended-spectrum β-lactamase SHV-12, RmtH and ISCR2 elements. ISCR2 elements and rmtH exhibit are unusual organization, suggesting a gene amplification due to the rolling-circle replication of ISCR2. We also identified a new hybrid toxin-antitoxin system in the backbone of the plasmid.

本研究报道了一株携带编码16S rRNA甲基转移酶基因rmtH的114kb质粒的完整序列。该质粒从黎巴嫩分离的产碳青霉烯酶肺炎克雷伯菌（Klebsiella pneumoniae）菌株中得到鉴定与表征。这是rmtH基因首次在质粒中被报道。该质粒携带有一个与新型复合转座子（composite transposon）相关的抗生素耐药岛（antibiotic resistance island），该复合转座子编码超广谱β-内酰胺酶（extended-spectrum β-lactamase）SHV-12、RmtH以及ISCR2元件。ISCR2元件与rmtH的排布方式较为特殊，提示二者可能因ISCR2的滚环复制（rolling-circle replication）发生了基因扩增。本研究还在该质粒的骨架中鉴定出一套全新的杂合毒素-抗毒素系统（hybrid toxin-antitoxin system）。