Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
Int J Med Microbiol. 2011 Dec;301(8):654-8. doi: 10.1016/j.ijmm.2011.09.003. Epub 2011 Oct 12.
A plasmid is defined as a double stranded, circular DNA molecule capable of autonomous replication. By definition, plasmids do not carry genes essential for the growth of host cells under non-stressed conditions but they have systems which guarantee their autonomous replication also controlling the copy number and ensuring stable inheritance during cell division. Most of the plasmids confer positively selectable phenotypes by the presence of antimicrobial resistance genes. Plasmids evolve as an integral part of the bacterial genome, providing resistance genes that can be easily exchanged among bacteria of different origin and source by conjugation. A multidisciplinary approach is currently applied to study the acquisition and spread of antimicrobial resistance in clinically relevant bacterial pathogens and the established surveillance can be implemented by replicon typing of plasmids. Particular plasmid families are more frequently detected among Enterobacteriaceae and play a major role in the diffusion of specific resistance genes. For instance, IncFII, IncA/C, IncL/M, IncN and IncI1 plasmids carrying extended-spectrum beta-lactamase genes and acquired AmpC genes are currently considered to be "epidemic resistance plasmids", being worldwide detected in Enterobacteriaceae of different origin and sources. The recognition of successful plasmids is an essential first step to design intervention strategies preventing their spread.
质粒被定义为一种双链、环状 DNA 分子，能够自主复制。根据定义，质粒不携带在非应激条件下宿主细胞生长所必需的基因，但它们具有系统，可以保证其自主复制，同时控制拷贝数，并确保在细胞分裂过程中的稳定遗传。大多数质粒通过存在抗菌药物抗性基因而赋予正向选择表型。质粒作为细菌基因组的一个组成部分而进化，提供了可以通过接合在不同来源和起源的细菌之间轻松交换的抗性基因。目前，采用多学科方法来研究临床相关细菌病原体中抗菌药物抗性的获得和传播，并且可以通过质粒复制子分型来实施既定的监测。特定的质粒家族在肠杆菌科中更频繁地被检测到，并且在特定抗性基因的扩散中起主要作用。例如，携带扩展谱β-内酰胺酶基因和获得的 AmpC 基因的 IncFII、IncA/C、IncL/M、IncN 和 IncI1 质粒，目前被认为是“流行抗性质粒”，在不同来源和起源的肠杆菌科中被全球检测到。识别成功的质粒是设计防止其传播的干预策略的重要第一步。
