School of Molecular Bioscience, The University of Sydney, NSW 2006, Australia.
J Antimicrob Chemother. 2012 Jun;67(6):1342-6. doi: 10.1093/jac/dks037. Epub 2012 Feb 20.
To determine the context and location of the bla(OXA-23) carbapenem-resistance gene and the structure of the resistance island in the chromosomal comM gene in a representative Australian global clone 2 (GC2) Acinetobacter baumannii isolate.
Long-range PCR was used to link genes and determine the organization of the resistance island. PCR amplicons were sequenced, and bioinformatic analysis identified features. Multilocus sequence typing (MLST) was performed.
The GC2 isolate A91 is sequence type (ST) ST92 (Oxford MLST scheme). It includes a 37 kb genomic resistance island, Tn6167, in the comM gene. At one end, Tn6167 carries Tn6022Δ1 interrupted by a novel insertion sequence, ISAba17. The sul2 (sulphonamide resistance) and strA-strB (streptomycin resistance) genes and tet(B) tetracycline resistance determinant are at the other end in the configuration ISAba1-sul2-CR2Δ-tetA(B)-tetR(B)-CR2-strB-strA with part of the tni end of a Tn6022-related transposon preceding them and an orf4 end following them. Transposon Tn2006 carrying bla(OXA-23) was found in an 11 kb region located between Tn6022Δ1 and the other resistance genes. The 17.6 kb Tn6166 from the GC2 reference strain A320/RUH134 can be derived from Tn6167 via a single deletion arising adjacent to Tn6022Δ1 and causing loss of a large central segment.
The transposons found in comM in the GC2 isolates A91 and A320 differ substantially from AbaR3-type islands, found predominantly in global clone 1 (GC1) isolates, in both resistance gene content and organization. However, the A. baumannii GC1 and GC2 clones have both acquired antibiotic resistance genes via their association with transposons that target comM.
确定具有代表性的澳大利亚全球克隆 2 (GC2) 鲍曼不动杆菌分离株中 bla(OXA-23) 碳青霉烯耐药基因的上下文和位置，以及染色体 comM 基因中耐药岛的结构。
使用长距离 PCR 将基因连接起来，并确定耐药岛的组织。对 PCR 扩增子进行测序，生物信息学分析鉴定特征。进行多位点序列分型 (MLST)。
GC2 分离株 A91 为 ST92（牛津 MLST 方案）。它在 comM 基因中包含一个 37 kb 的基因组耐药岛 Tn6167。在一端，Tn6167 携带 Tn6022Δ1 被一个新的插入序列 ISAba17 打断。sul2（磺胺类耐药）和 strA-strB（链霉素耐药）基因和 tet(B) 四环素耐药决定子位于另一端，在 ISAba1-sul2-CR2Δ-tetA(B)-tetR(B)-CR2-strB-strA 构型中，它们前面是 Tn6022 相关转座子的 tni 端的一部分，后面是 orf4 端。在位于 Tn6022Δ1 和其他耐药基因之间的 11 kb 区域中发现了携带 bla(OXA-23) 的转座子 Tn2006。GC2 参考菌株 A320/RUH134 的 17.6 kb Tn6166 可通过 Tn6022Δ1 附近发生的单个缺失产生，该缺失导致大片段中央缺失，从而从 Tn6167 衍生而来。
GC2 分离株 A91 和 A320 中 comM 中的转座子在耐药基因含量和组织方面与主要在全球克隆 1 (GC1) 分离株中发现的 AbaR3 型岛屿有很大不同。然而，GC1 和 GC2 克隆的鲍曼不动杆菌都通过与靶向 comM 的转座子的关联获得了抗生素耐药基因。
