[Molecular epidemiology and resistance mechanisms of tigecycline-non-susceptible Acinetobacter baumannii]

Sheng Wu Gong Cheng Xue Bao. 2018 Aug 25;34(8):1218-1225. doi: 10.13345/j.cjb.180196.
[Article in Chinese]

Abstract

To investigate the resistance mechanisms of tigecycline-non-susceptible Acinetobacter baumannii and for providing the evidence of the control of nosocomial infection and rational use of antibiotics. The minimum inhibitory concentrations (MICs) of 94 non repetitive tigecycline-non-susceptible A. baumannii from 20 hospitals in 12 cities of China were determined by agar dilution method and broth microdilution method. The molecular epidemiology was studied by Multilocus sequence typing (MLST) and eBURST software. PCR and sequencing techniques were used to analyze the resistance genes (blaOXA-40-like, blaOXA-58-like, blaOXA-23-like, blaOXA-51-like, blaNDM-1), ISAba1, and the mutation sites of adeR, adeS, and trm. The activity of polymyxin B and minocyclinem against tigecycline-non-susceptible A. baumannii were 100% and 25.5%, respectively. The sensitivities of other antibiotics were less than 3.5%, and the sensitivities of imipenem and meropenem totigecycline-nonsusceptible A. baumannii were only 1.1%. A total of 12 ST types were identified, including ST195 (45, 47.9%), ST208 (19, 20.2%) and ST457 (10, 10.6%). EBURST analysis found that 8 of the ST types belonged to the clone complex 92 (Clonal Complex 92, CC92). The blaOXA-23-like type carbapenem gene was identiefied in 93 strains (99% positive); and none of the strains contained the blaNDM-1 gene. The detection rates of adeR and adeS were 73.4% and 91.5% respectively and high frequency mutation sites were located in adeR (Asp26Asn) and adeS (Ala97Glu); The ISAba1 located upstream of the adeS gene was detected in 12 strains of A. baumannii, mainly from the northern region of China. The 240 nucleotide deletion of the trm gene caused a frameshift leading to a premature stop. So the tigecycline-non-susceptible A. baumannii showed high resistance against most antibiotics except polymyxin B. The deletion and mutation of adeR, adeS and trm were the main resistant mechanisms in tigecycline-non-susceptible A. baumannii in China.

为探讨替加环素不敏感鲍曼不动杆菌Acinetobacter baumannii 的耐药机制,为院内感染控制及临床合理用药提供理论依据,采用琼脂稀释法和微量肉汤稀释法检测全国多中心12 个城市20 家医院临床分离的94 株非重复的替加环素不敏感鲍曼不动杆菌的最低抑菌浓度 (Minimum inhibitory concentration,MIC),应用多位点序列分型 (Multilocus sequence typing,MLST) 技术进行分子流行病学研究,应用eBURST 软件对MLST 结果进行分析;用PCR 和测序技术分析常见耐药基因 (blaOXA-40-like、blaOXA-58-like、blaOXA-23-like、blaOXA-51-like、blaNDM-1),与替加环素耐药相关的外排泵调控基因adeR 和adeS 的突变位点、trm 的突变位点。经检测94 株鲍曼不动杆菌除对多粘菌素B 100%敏感、对米诺环素敏感率25.5%外,其他抗菌药物的敏感率均低于3.5%,亚胺培南和美罗培南敏感率均只有1.1%。MLST 分型得到12 种ST 分型,以ST195 (45 株,47.9%)、ST208 (19 株,20.2%) 和ST457 (10 株,10.6%) 为主,eBURST 分析发现其中8 个ST 型均属于克隆复合体92 (Clonal Complex 92,CC92);99%菌株blaOXA-23-like 型碳青霉烯酶基因阳性;均未扩增出blaNDM-1 基因;外排泵调控基因adeR 和adeS 的检出率分别是73.4%和91.5%,Asp26Asn 和Ala97Glu分别为adeR 和adeS 的高频突变位点;在12 株鲍曼不动杆菌中检测到了adeS基因的ISAba1,以北部地区为主;trm 基因均在第240 位核苷酸发生缺失突变。综上所述,替加环素不敏感鲍曼不动杆菌对除多粘菌素B 外的大多数抗菌药物具有很高的耐药性,AdeABC 外排泵上游的双组分调控系统adeR和adeS 的缺失和突变,trm 缺失突变是导致鲍曼不动杆菌对替加环素敏感性降低的主要原因。.

Keywords: Acinetobacter baumannii; adeRS; multilocus sequence typing; tigecycline.

MeSH terms

  • Acinetobacter Infections / drug therapy
  • Acinetobacter baumannii / drug effects*
  • Acinetobacter baumannii / genetics
  • Anti-Bacterial Agents / pharmacology*
  • China
  • Drug Resistance, Bacterial*
  • Humans
  • Microbial Sensitivity Tests
  • Molecular Epidemiology
  • Multilocus Sequence Typing
  • Tigecycline / pharmacology*
  • beta-Lactamases / genetics

Substances

  • Anti-Bacterial Agents
  • Tigecycline
  • beta-Lactamases