103个mcr质粒的结构与特征

黏菌素是治疗碳青霉烯类耐药菌感染的最后一线药物。然而,近年来在许多致病菌中发现质粒介导的黏菌素耐药基因mcr传播,降低了黏菌素的有效性,对公众健康构成了威胁。为探讨可能影响黏菌素耐药性传播的质粒特征,基于mcr质粒的完成图,共分析了2015—2018年GenBank收录的103个携带mcr的完整质粒序列。结果表明:质粒主要来源于中国,大肠埃希菌为主要携带者;IncI2和IncX4是最主要的复制子类型,IncHI2是携带有多个耐药基因质粒的优势复制子类型;sul3、aadA1与mcr基因在质粒中共存的概率最高。另外还发现,95.14%的质粒含有抗消毒剂或重金属抗性基因。除ISApl1外,IS26插入序列出现频率最高。18.45%的质粒具有接合转移元件,包括oriT、松弛酶(relaxase)、T4CP和T4SS。本文重点指出了耐药基因交叉抗性和重金属的共选择作用,为更好地控制黏菌素耐药性提供了思路。

Structures and characteristics of 103 plasmids carrying mcr gene

Colistin is the last first-line drug in the treatment of carbapenem-resistant pathogens infection. However, the widespread of plasmid mediated mcr gene which involved colistin resistance had reduced the effectiveness and posed a threat to public health. The purpose of this study was to summarize the complete plasmids bearing mcr and explore plasmid characteristics that might affect the spread of colistin resistance. A total of 103 complete plasmid sequences carrying mcr which were released in GenBank from 2015 to 2018 were analyzed. The results showed that the main plasmids were from China and Escherichia coli was the main host. IncI2 and IncX4 were the most important replicon types, and IncHI2 was the dominant type of plasmids with multiple resistance genes. Meanwhile, 95.14% of the plasmids contained antibacterial biocide or heavy metal resistance genes. Except for ISApl1, the frequency of IS26 was the highest. 18.45% of them had conjugated transfer elements, including oriT, relaxase, T4CP and T4SS. This study emphasized the co-selection of antibiotics and heavy metals, which provided landscape for better control of colistin resistance.