老年患者耐碳青霉烯类鲍曼不动杆菌分布研究

The distribution of carbapenem-resistant acinetobacter baumannii in older adults

目的研究北京地区耐碳青霉烯类的鲍曼不动杆菌（CRAB）分子分型的主要型别及分布情况。方法收集北京地区2010-2014年医院60岁以上的老年患者临床分离的非重复耐碳青霉烯类的CRAB78株，用微量稀释法测定11种抗菌药物的药敏试验，采用改良的Hodge试验初筛碳青霉烯酶，多重PCR分析鲍曼不动杆菌OXA-23-like、OXA24-like、OXA-51-like、OXA-58-like、IMP-1、VIM-2碳青霉烯酶基因，检测OXA-23-like、OXA-51-like插入序列IsAbal，采用三位点序列分型（3LST）对碳青霉烯类的鲍曼不动杆菌同源性初步分型，根据药敏试验、碳青霉烯酶基因分型、3LST初筛结果和医院分布选出22株进行多位点序列分型（MLST）。结果78株CRAB中OXA酶基因检测显示，所有菌株均携带OXA-51-like，74株检出OXA23-like（94．8％），OXA-23like阳性的菌株其ISAbal—OXA-23产物均为阳性。在检测的5种β-内酰胺酶基因中74株检出高产头孢菌素酶基因（AmpC）占94．8％；50株β-内酰胺酶型基因（TEM-1）占64．1％；5株超广谱β内酰胺酶型基因（PER-1）占6．4％；48株同时检出TEM-1、AmpC酶基因占61．5％；3株同时检出TEM1、AmpC酶和PER-1型基因。使用3LST进行分型初筛，74株是Group分型Ⅰ型，属于欧洲克隆谱系Ⅱ；MLST分型中发现的6个ST型中，其中ST195、ST208、ST218、ST368均属于克隆复合体92（CC92）；ST103型、ST500型为国内首次发现的两个新型别。结论CC92克隆群为北京地区CRAB主要分布克隆株，属于经典的欧洲克隆谱系Ⅱ，其插入序列ISAbal介导OXA-23型碳青霉烯酶是北京地区鲍曼不动杆菌对碳青霉烯酶耐药主要的分子机制。多数菌株同时检出AmpC酶和TEM1型一内酰胺酶基因。在新发现的2种型别中，主要是CC103克隆复合体。

Objective To study the main types and their distribution of molecular typing of carbapenem-resistant Acinetobacter baumannii （CRAB）in Beijing. Methods Seventy eight non repeated CRAB strains were isolated and collected from patients aged over 60 years in hospitals in Beijing from 2010 to 2014. The drug susceptibilities of 11 antimicrobial agents were tested by microdilution method. A modified Hodge assay was used to preliminarily screen the carbapenemases. A multiplex PCR assay was used for detection of the carbapenemases genes： OXA 23-like, OXA 24-like, OXA-51-1ike, OXA 58-like, IMP 1, and VIM 2 of Acinetobacter baumannii. We also detected the insertion sequence IsAbal of OXA-23-1ike and OXA-51 like, and the preliminary classification of homology of carbapenem-resistant Aeinetobaeter baumannii （CRAB）was conducted by 3LST technique. According to the drug susceptibility, carbapenemases gene typing, 3LST primary screen, and hospital distribution,22 strains were selected to conduct MLST classification. Results The test of OXA enzyme gene in 78 strains of CRAB showed that all the strains （100%）carried oxa-51-1ike, and 74/78 strains（94.8 %）carried oxa-23 like. Additionally, all products of ISAbal-oxa-23 were positive in OXA 23-like positive strains. In the examined five β-lactamase genes, 74 strains （94.8%） showed positive AmpC gene; 50 strains （64. 1%） showed positive TEM-1 genel 5 strains （6.4%） showed positive PER-1 gene;48 strains（61.5%）showed positive genes of TEM-1 and AmpC and 3 strains showed positive genes of TEM-1, Amp C, and PER 1. By using 3LST technique for preliminary classification,we found 74 strains were in type Ⅰ of group types belonging to the European Ⅱ cloning spectrum. Of the six ST types found in MLST classification, the ST195, ST208, ST218 and ST368 belonged to the clone complex 92（CC92） ;the ST103 and ST500 were two newly discovered types in Chinese population. Conclusions CC92 clone cluster is the major epidemic strain of CRAB in Beijing,which belongs to the classic European Ⅱ cloning spectrum,and its insertion sequence, Abalinduced OXA-23-1ike carbapenemases is the major molecular of carhapenem-resistant Acinetobacter baumannii（CRAB） in Beijing. Both AmpC and TEM-type 1 β-lactamase genes are detected to be positive in most of strains. The newly discovered two types are mainly CC103 clone complex.