Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy.
Int J Med Microbiol. 2013 Aug;303(6-7):305-17. doi: 10.1016/j.ijmm.2013.02.008. Epub 2013 Mar 13.
Production of extended-spectrum β-lactamases (ESBLs) is the principal mechanism of resistance to oxyimino-cephalosporins evolved by members of the family Enterobacteriaceae. Among the several ESBLs emerged among clinical pathogens, the CTX-M-type enzymes have proved the most successful in terms of promiscuity and diffusion in different epidemiological settings, where they have largely replaced and outnumbered other types of ESBLs. Originated by the capture and mobilization of chromosomal β-lactamase genes of strains of Kluyvera species, the blaCTX-M genes have become associated with a variety of mobile genetic elements that have mediated rapid and efficient inter-replicon and cell-to-cell dissemination involving highly successful enterobacterial lineages (e.g. Escherichia coli ST131 and ST405, or Klebsiella pneumoniae CC11 and ST147) to yield high-risk multiresistant clones that have spread on a global scale. The CTX-Mβ-lactamase lineage exhibits a striking plasticity, with a large number of allelic variants belonging in several sublineages, which can be associated with functional heterogeneity of clinical relevance. This review article provides an update on CTX-M-type ESBLs, with focus on structural and functional diversity, epidemiology and clinical significance.
产超广谱β-内酰胺酶（ESBLs）是肠杆菌科成员对氧亚氨基头孢菌素产生耐药性的主要机制。在临床病原体中出现的几种 ESBL 中，CTX-M 型酶在不同的流行病学环境中表现出最大的混杂性和扩散性，它们在很大程度上取代了其他类型的 ESBL 并超过了其他类型的 ESBL。CTX-M 基因最初是由克吕沃尔氏菌属菌株的染色体β-内酰胺酶基因捕获和移动而来，已与多种移动遗传元件相关联，这些元件介导了高效的复制子间和细胞间传播，涉及到高度成功的肠杆菌科谱系（例如大肠杆菌 ST131 和 ST405，或肺炎克雷伯菌 CC11 和 ST147），从而产生了具有全球传播风险的多药耐药克隆。CTX-Mβ-内酰胺酶谱系表现出显著的可塑性，有大量属于几个亚谱系的等位基因变异体，这些变异体可能与临床相关的功能异质性有关。本文综述了 CTX-M 型 ESBL 的最新研究进展，重点介绍了其结构和功能多样性、流行病学和临床意义。
