Site-Specific Recombination at XerC/D Sites Mediates the Formation and Resolution of Plasmid Co-integrates Carrying a bla(OXA-58)- and TnaphA6-Resistance Module in Acinetobacter baumannii.
Site-Specific Recombination at XerC/D Sites Mediates the Formation and Resolution of Plasmid Co-integrates Carrying a bla(OXA-58)- and TnaphA6-Resistance Module in Acinetobacter baumannii.
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DOI：
10.3389/fmicb.2018.00066
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发表时间：
2018
影响因子：
5.2
通讯作者：
Viale AM
中科院分区：
文献类型：
--
作者：
Cameranesi MM;Morán-Barrio J;Limansky AS;Repizo GD;Viale AM
不动杆菌属的成员具有独特的质粒型，这为获得、进化和传播抗菌素耐药结构提供了有效的平台。许多质粒携带的抗性结构被短DNA序列包围，这些短DNA序列为宿主XerC和XerD位点特异性酪氨酸重组酶(XerC/D样位点)提供潜在的识别位点。然而，这些位点是否在重组中活跃以及它们如何帮助动员相关的抗性结构仍然知之甚少。在这里，我们表征了鲍曼不动杆菌Ab242携带的质粒，该菌株属于ST104(牛津方案)，它产生一种OXA-58型碳青霉烯类水解型β-内酰胺酶(CHDL型)。质粒测序和复制、稳定性和适应性模块的鉴定表明，在Ab242中存在三个缺乏自我转移功能的新质粒，分别命名为pAb242_9、pAb242_12和pAb242_25。其中，只有pAb242_25携带一个由ISAba825-blaOXA-58排列和TnaphA6转座子组成的适应模块，整个结构对碳青霉烯类和氨基糖苷类抗生素同时耐药。Ab242含有几个类似XerC/D的位点，其中大部分位于pAb242_25附近或位于上述适应模块内。用Ab242质粒电转化农杆菌敏感细胞，亚胺培南筛选表明，转化质粒形式是pAb242_25和pAb242_12融合形成的共整合形式。进一步的克隆和测序鉴定表明，pAb242_25和pAb242_12上的XerC/D位点为介导这两个质粒融合的分子间特异性重组反应提供了活性姊妹对。此外，还发现所产生的共整合在融合过程中产生的新的XerC/D位点上进行了分子内拆分，从而再生了原始的pAb242_25和pAb242_12质粒。这些观察提供了第一个证据，表明鲍曼不动杆菌质粒中的XerC/D样位点可以为介导分子间融合和分子内分辨的特定位点重组提供活性对。总体结果揭示了鲍曼不动杆菌质粒的进化动态，以及导致碳青霉烯类和其他抗生素耐药性的遗传结构在临床不动杆菌群体中传播的潜在机制。
Members of the genus Acinetobacter possess distinct plasmid types which provide effective platforms for the acquisition, evolution, and dissemination of antimicrobial resistance structures. Many plasmid-borne resistance structures are bordered by short DNA sequences providing potential recognition sites for the host XerC and XerD site-specific tyrosine recombinases (XerC/D-like sites). However, whether these sites are active in recombination and how they assist the mobilization of associated resistance structures is still poorly understood. Here we characterized the plasmids carried by Acinetobacter baumannii Ab242, a multidrug-resistant clinical strain belonging to the ST104 (Oxford scheme) which produces an OXA-58 carbapenem-hydrolyzing class-D β-lactamase (CHDL). Plasmid sequencing and characterization of replication, stability, and adaptive modules revealed the presence in Ab242 of three novel plasmids lacking self-transferability functions which were designated pAb242_9, pAb242_12, and pAb242_25, respectively. Among them, only pAb242_25 was found to carry an adaptive module encompassing an ISAba825-blaOXA-58 arrangement accompanied by a TnaphA6 transposon, the whole structure conferring simultaneous resistance to carbapenems and aminoglycosides. Ab242 plasmids harbor several XerC/D-like sites, with most sites found in pAb242_25 located in the vicinity or within the adaptive module described above. Electrotransformation of susceptible A. nosocomialis cells with Ab242 plasmids followed by imipenem selection indicated that the transforming plasmid form was a co-integrate resulting from the fusion of pAb242_25 and pAb242_12. Further characterization by cloning and sequencing studies indicated that a XerC/D site in pAb242_25 and another in pAb242_12 provided the active sister pair for the inter-molecular site-specific recombination reaction mediating the fusion of these two plasmids. Moreover, the resulting co-integrate was found also to undergo intra-molecular resolution at the new pair of XerC/D sites generated during fusion thus regenerating the original pAb242_25 and pAb242_12 plasmids. These observations provide the first evidence indicating that XerC/D-like sites in A. baumannii plasmids can provide active pairs for site-specific recombination mediating inter-molecular fusions and intra-molecular resolutions. The overall results shed light on the evolutionary dynamics of A. baumannii plasmids and the underlying mechanisms of dissemination of genetic structures responsible for carbapenem and other antibiotics resistance among the Acinetobacter clinical population.