1株LpsB突变致多黏菌素B耐药鲍曼不动杆菌的全基因测序分析

Whole gene sequencing analysis for a polymyxin B resistant strain of Acinetobacter baumannii with LpsB mutation

目的研究1株多黏菌素B高水平耐药的多重耐药鲍曼不动杆菌的全基因组测序的分子特点。方法将1株分离自脑脓肿患者脑脊液标本的多黏菌素高水平耐药鲍曼不动杆菌Z198株作为目标研究菌,通过Nanopore PromethION和Illumina NovaSeq PE150测序平台对其进行全基因组测序,再通过各数据库进行比对分析检测菌株的多位点序列分型(MLST)、抗菌药物耐药基因、毒力基因,同时采用Circos软件对样品基因组组装和注释结果进行可视化分析。Z198基因组上交NCBI数据库。结果全基因组测序发现该菌株含有1个染色体、1个固有质粒,11个基因岛、4个前噬菌体。通过数据库比对,本菌为ST2型,共携带高达34种抗菌药物耐药基因,主要为LpsB、bla OXA-23、bla_(OXA-66)、bla_(ADC-73)等,同时含有OmpA、磷脂酶C、包膜、溶血素、生物膜调控系统等19种主要毒力因子。结论本研究检出1例LpsB四点突变导致多黏菌素B耐药的鲍曼不动杆菌。该菌株同时携带多重耐药基因及毒力因子。多黏菌素耐药鲍曼不动杆菌外膜脂质修饰的耐药机制及分子流行病学需高度持续关注。

Objective To analyze the molecular characteristics of a multidrug-resistant Acinetobacter baumannii strain with high resistant level for polymyxin B in whole-genome sequencing.Methods A polymyxin B high-level resistant strain of Acinetobacter baumannii Z198 isolated from cerebrospinal fluid samples of a brain abscess patients was served as the target strain.The whole genome of the strain was sequenced by Nanopore PromethION and Illumina NovaSeq PE150 sequencing platform,and then the identification of multilocus sequence typing(MLST),antimicrobial resistance genes and virulence genes of the strains were performed by comparative analysis for the sequence of the whole genome with various databases.Circos software was used for visualization analysis of the genome assembly and annotation results.The Z198 strain genome was submitted to NCBI database.Results Whole genome sequencing revealed that the strain contained one chromosome,one intrinsic plasmid,11 gene islands and 4 prophages.According to the results of comparative analysis for various database,this strain should be included in ST2 type,carrying up to 34 antimicrobial resistance genes,mainly LpsB,bla OXA-23,bla_(OXA-66),bla_(ADC-73),etc.and containing 19 major virulence factors such as OmpA,phospholipase C,envelope,hemolysin and biofilm regulatory systems.Conclusion We identified a strain of Acinetobacter baumannii with a four-point LpsB mutation resulting in polymyxin B resistance,carrying multiple resistance genes and virulence factors.The mechanism of drug resistance and molecular epidemiology of lipid modification in the outer membrane of polymyxin-resistant Acinetobacter baumannii certainly deserve intensive and continuous attention.