The ithree institute, University of Technology Sydney, Ultimo, New South Wales, Australia.
School of Life and Environmental Sciences, The University of Sydney, New South Wales, Australia.
PLoS One. 2018 Sep 27;13(9):e0204357. doi: 10.1371/journal.pone.0204357. eCollection 2018.
Four plasmids ranging in size from 4.7 to 44.7 kb found in the extensively antibiotic resistant Acinetobacter baumannii isolate D36 that belongs to lineage 2 of global clone 1 were examined. D36 includes two cryptic plasmids and two carrying antibiotic resistance genes. The smallest plasmid pD36-1 (4.7 kb) carries no resistance genes but includes mobA and mobC mobilisation genes related to those found in pRAY* (pD36-2, 6,078 bp) that also carries the aadB gentamicin, kanamycin and tobramycin resistance gene cassette. These two plasmids do not encode a Rep protein. Plasmid pRAY* was found to be mobilised at high frequency by the large conjugative plasmid pA297-3 but a pRAY* derivative lacking the mobA and mobC genes was not. The two larger plasmids, pD36-3 and pD36-4, encode Rep_3 family proteins (Pfam1051). The cryptic plasmid pD36-3 (6.2 kb) has RepAci1 and pD36-4 (44.7 kb) encodes two novel Rep_3 family proteins suggesting a co-integrate. Plasmid pD36-4 includes the sul2 sulfonamide resistance gene, the aphA1a kanamycin/neomycin resistance gene in Tn4352::ISAba1 and a mer module in a hybrid Tn501/Tn1696 transposon conferring resistance to mercuric ions. New examples of dif modules flanked by pdif sites (XerC-XerD binding sites) that are part of many A. baumannii plasmids were also identified in pD36-3 and pD36-4 which carry three and two dif modules, respectively. Homologs of three dif modules, the sup sulphate permease module in pD36-3, and of the abkAB toxin-antitoxin module and the orf module in pD36-4, were found in different contexts in diverse Acinetobacter plasmids, consistent with module mobility. A novel insertion sequence named ISAba32 found next to the pdif site in the abkAB dif module is related to members of the ISAjo2 group which also are associated with the pdif sites of dif modules. Plasmids found in D36 were also found in some other members of GC1 lineage 2.
检测了在广泛耐药的鲍曼不动杆菌分离株 D36 中发现的 4 个大小在 4.7 到 44.7 kb 之间的质粒，该分离株属于全球克隆 1 谱系 2。D36 包括两个隐秘质粒和两个携带抗生素耐药基因的质粒。最小的质粒 pD36-1（4.7 kb）不携带耐药基因，但包含与 pRAY*（pD36-2，6078 bp）中发现的 mobA 和 mobC 移动基因有关的 mobA 和 mobC 移动基因，后者还携带 aadB 庆大霉素、卡那霉素和妥布霉素耐药基因盒。这两个质粒不编码 Rep 蛋白。发现大的接合质粒 pA297-3 可高频转移质粒 pRAY*，但缺乏 mobA 和 mobC 基因的 pRAY*衍生物则不能。两个较大的质粒 pD36-3 和 pD36-4 编码 Rep_3 家族蛋白（Pfam1051）。隐秘质粒 pD36-3（6.2 kb）有 RepAci1，pD36-4（44.7 kb）编码两个新的 Rep_3 家族蛋白，提示存在共整合。质粒 pD36-4 包含 sul2 磺胺类耐药基因、Tn4352::ISAba1 中的 aphA1a 卡那霉素/新霉素耐药基因和位于 Tn501/Tn1696 转座子中的 mer 模块，该转座子赋予对汞离子的抗性。在 pD36-3 和 pD36-4 中还发现了新的 dif 模块侧翼的 pdif 位点（XerC-XerD 结合位点），这些模块是许多鲍曼不动杆菌质粒的一部分，它们分别携带三个和两个 dif 模块。在不同的 context 中发现了 pD36-3 中的三个 dif 模块的同源物，即 sup 硫酸盐渗透酶模块，以及 pD36-4 中的 abkAB 毒素-抗毒素模块和 orf 模块，这与模块的移动性一致。在 abkAB dif 模块的 pdif 位点旁边发现了一个名为 ISAba32 的新插入序列，它与 ISAjo2 组的成员有关，后者也与 dif 模块的 pdif 位点有关。在 D36 中发现的质粒也存在于其他一些 GC1 谱系 2 的成员中。
