碳青霉烯耐药鲍曼不动杆菌的质粒特征

Plasmid characteristics of carbapenem-resistant Acinetobacter baumannii

    摘要
  • 摘要:
    目的 分析多中心收集的碳青霉烯类耐药鲍曼不动杆菌（CRAB）临床分离株所携带质粒的结构特征，系统解析耐药基因及相关遗传元件的分布规律，阐明质粒介导耐药性传播的潜在机制。
    方法 收集1999－2018年我国北京、天津、浙江、江苏、辽宁、黑龙江、山东、广东、湖北、陕西、上海、新疆等12个省市自治区的84株CRAB临床分离株，经Illumina与PacBio测序联合组装获得112个完整质粒序列。利用生物信息学方法分析质粒类型和携带的耐药基因、毒力基因、Ⅱ型毒素-抗毒素（TA）系统、pdif位点及噬菌体相关序列。
    结果 84株CRAB中ST2型菌株占绝大多数（81株）。112个质粒中，36个（32.14%）携带耐药基因，主要包括blaOXA-23、blaOXA-58、blaOXA-72、blaTEM-1和blaPER-1，其中blaOXA-23检出率最高（33个质粒），主要集中于T2型（25条）和T1型（7条）。另有2个质粒（1.78%）携带毒力基因（adeG与hemO）。共39个质粒（34.82%）检出Ⅱ型TA系统，均编码RelE样毒素和XRE样抗毒素蛋白。另有3个质粒携带pdif位点，22个质粒含噬菌体相关序列。
    结论 CRAB中质粒定位的blaOXA-23检出率较高，并主要集中于T2型和T1型质粒。部分质粒同时携带多种耐药基因。毒力基因与Ⅱ型TA系统的检出提示耐药质粒在耐药播散的同时可能会影响细菌的毒力。部分质粒含pdif位点和噬菌体相关序列，表明耐药质粒可能通过多途径播散。

     

    Abstract:
    OBJECTIVE  To analyze the structural characteristics of plasmids carried by clinical isolates of carbapenem-resistant Acinetobacter baumannii （CRAB） collected from multiple centers, to systematically dissect the distribution patterns of resistance genes and related genetic elements, and to elucidate the potential mechanisms of underlying plasmid-mediated resistance transmission.
    METHODS  A total of 84 clinical isolates of CRAB from 12 provinces/municipalities in China, including Beijing, Tianjin, Zhejiang, Jiangsu, Liaoning, Heilongjiang, Shandong, Guangdong, Hubei, Shaanxi, Shanghai, and Xinjiang, were collected from 1999 to 2018. A total of 112 complete plasmid sequences were obtained through hybrid assembly of Illumina and PacBio sequencing data. Bioinformatics analyses were performed to characterize plasmid types, carried resistance genes, virulence genes, type II toxin-antitoxin （TA） systems, pdif loci and phage-related sequences.
    RESULTS  Among the 84 CRAB isolates, ST2 type strains accounted for the vast majority （n=81）. Of the 112 plasmids, 36 （32.14%） carried resistance genes, primarily including blaOXA-23, blaOXA-58, blaOXA-72, blaTEM-1 and blaPER-1. Among them, blaOXA-23 exhibited the highest detection rate, being present in 33 plasmids, which were mainly concentrated in type T2 （n=25） and type T1 （n=7）. Additionally, 2 plasmids （1.78%） carried virulence genes adeG and hemO. Type II TA systems were detected in 39 plasmids （34.82%）, all of which encoded RelE-like toxins and XRE-like antitoxins. Furthermore, 3 plasmids carried pdif loci, and 22 contained phage-related sequences.
    CONCLUSIONS The plasmid-borne blaOXA-23 gene is detected at a high frequency in CRAB and is predominantly found in T2 and T1 plasmid types. Certain plasmids carry multiple resistance genes simultaneously. The presence of virulence genes and type II TA systems suggests that resistance plasmids may influence bacterial virulence alongside disseminating resistance. Some plasmids contain pdif loci and phage-related sequences, indicating that resistant plasmids may spread through multiple pathways.

     

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