Department of Respiratory Diseases, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, People's Republic of China.
J Antimicrob Chemother. 2010 Apr;65(4):644-50. doi: 10.1093/jac/dkq027. Epub 2010 Feb 12.
In this study, multilocus sequence typing (MLST) was used to describe the genetic backgrounds of carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-susceptible A. baumannii (CSAB) from multiple cities of China.
One hundred and fifty-two CRAB and 74 CSAB isolates obtained from 16 cities of China were selected for molecular characterization by MLST. eBURST was used to cluster sequence types (STs) into clonal complex (CCs) and infer evolutionary descent. PCR was used to detect carbapenemase-encoding genes and bla(AmpC) with the upstream element ISAba1.
CSAB showed more diverse genetic backgrounds than CRAB since 36 distinct STs were identified in CSAB while only 8 STs were identified in CRAB. ST22 and its three single-locus variants, all clustered into CC22, were the most prominent STs, accounting for 86.8% of CRAB and 45.9% of CSAB, distributed in all 16 cities and possessing more noticeable antibiotic resistance than other STs. PCR amplification was positive for bla(OXA-23) in most CRAB isolates but negative in CSAB isolates. The presence of ISAba1 upstream of bla(AmpC) was variable in distinct STs of CRAB. eBURST reveals that CC22 is the largest group in the Pubmlst database, which also contains ST6 previously identified in a European clone II isolate as a member of a subgroup of CC22.
We describe the wide dissemination of CRAB CC22 in China. The close relatedness between CC22 and European clone II implies the probable global spread of CC22. It is inferred that ST22-CSAB evolves to ST22-CRAB through acquiring bla(OXA-23) as a determinative factor.
本研究采用多位点序列分型（MLST）方法描述中国多个城市耐碳青霉烯鲍曼不动杆菌（CRAB）和碳青霉烯敏感鲍曼不动杆菌（CSAB）的遗传背景。
选择来自中国 16 个城市的 152 株 CRAB 和 74 株 CSAB 分离株进行分子特征分析，采用 MLST 将序列型（ST）聚类为克隆复合体（CC）并推断进化关系。PCR 检测碳青霉烯酶编码基因和 bla（AmpC），并带有上游元件 ISAba1。
CSAB 的遗传背景比 CRAB 更为多样化，因为在 CSAB 中鉴定出 36 个不同的 ST，而在 CRAB 中仅鉴定出 8 个 ST。ST22 及其三个单一位点变体，均聚类到 CC22，是最主要的 ST，分别占 CRAB 的 86.8%和 CSAB 的 45.9%，分布于所有 16 个城市，其抗生素耐药性比其他 ST 更为显著。大多数 CRAB 分离株 bla(OXA-23)的 PCR 扩增呈阳性，但 CSAB 分离株呈阴性。CRAB 不同 ST 中 bla(AmpC)上游 ISAba1 的存在情况各不相同。eBURST 显示 CC22 是 Pubmlst 数据库中最大的群组，其中还包含之前在欧洲克隆 II 分离株中鉴定出的 ST6，作为 CC22 亚群的成员。
我们描述了 CRAB CC22 在我国的广泛传播。CC22 与欧洲克隆 II 密切相关，暗示 CC22 可能在全球范围内传播。推断 ST22-CSAB 通过获得 bla(OXA-23)作为决定因素演变为 ST22-CRAB。
