耐碳青霉烯类鲍氏不动杆菌碳青霉烯酶基因型及插入序列ISAba1研究

目的了解耐碳青霉烯类药物鲍氏不动杆菌的临床分布及耐药特征,探讨插入序列ISAba1和碳青霉烯酶与其耐药的关系。方法收集270株耐碳青霉烯类药物的鲍氏不动杆菌,K-B法检测菌株的药物敏感性;改良Hodge试验检测碳青霉烯酶;双纸片协同试验检测金属酶;多重PCR检测OXA-51、OXA-23、OXA-58、OXA-24、IMP、VIM、SIM,PCR检测ISAbal-OXA-23、ISAbal-OXA-51基因并进行测序分析;采用WHONET 5.6软件对菌株药敏结果进行统计分析。结果在检测的18种药物中,14种药物耐药率超过90.0%,哌拉西林耐药率最高为100.0%,头孢哌酮/舒巴坦的耐药率最低为48.9%;改良Hodge试验阳性156株,阳性率57.8%;金属酶表型检测均为阴性;270株菌均检测到了OXA-51基因,267株菌检测到OXA-23基因,1株检测到OXA-58基因,未检测到OXA-24、IMP、VIM、SIM基因;267株菌的OXA-23基因上游均检测到插入序列ISAbal,所有OXA-51基因上游均未检测到ISAbal。结论耐碳青霉烯类药物鲍氏不动杆菌耐药十分严重;OXA-51和OXA-23型碳青霉烯酶是本地区鲍氏不动杆菌的主要碳青霉烯酶;ISAba1常在OXA-23基因上游出现,ISAbalOXA-23是鲍氏不动杆菌对碳青霉烯类药物耐药的重要机制。     

Silent mutations in ribosomal protein genes are associated with high-risk clones of carbapenem-resistant Acinetobacter baumannii prevalent in Brazil

ObjectivesTo analyze the relationship of ribosomal protein mutations and clonality of high-risk clones Acinetobacter baumannii.MethodsSeventy-nine carbapenem-resistant A. baumannii were subjected to whole-genome sequencing (Illumina NextSeq), and codifying sequences of ribosomal proteins were extracted and screened for mutations. MALDI-TOF MS analysis (Bruker Biotyper) and Spectra data from MALDI-TOF was employed to generate a dendrogram based on principal component analysis (PCA) data. Clones were identified by Multilocus sequencing typing (MLST) based on WGS.ResultsRibosomal RNA protein sequences extracted from the genomes identified mutations that were associated with clonal complexes, but most of them were silent. PCA did not cluster the isolates according to their clonality identified by MLST.ConclusionsBy comparing the nucleotide and amino acid sequences of diversified A. baumannii, and Bruker Biotyper profiles, we showed that silent mutations in ribosomal RNA nucleotides are associated with clonal complexes, but since most of the mutations were silent, MALDI-TOF MS raw data was not a useful tool for typing the high-risk clones of this species.     

Emergence and spread of carbapenem-resistant Acinetobacter baumannii sequence type 191 in a Korean hospital

Emergence and spread of specific carbapenem-resistant Acinetobacter baumannii (CRAB) clones cause a serious therapeutic problem. This study was aimed to investigate the clonal diversity and genetic basis of antimicrobial resistance among the 69 CRAB isolates from 2009 to 2010 in a Korean hospital. All CRAB isolates were found to be sequence type (ST) 2 using the Institute Pasteur’s multilocus sequence typing (MLST) scheme, but classified into two sequence groups and nine pulsotypes. Fifty-six CRAB isolates belonging to two main pulsotypes were found to be ST191 using the Bartual’s MLST scheme. All CRAB isolates showed an extensively drug-resistant phenotype. The bla_OXA-51/bla_OXA-23, bla_AmpC/bla_PER-1 and armA genes were largely responsible for resistance to carbapenems, extended-spectrum β-lactams and aminoglycosides, respectively. The first CRAB strains identified in 2005 in this hospital were found to be ST2 using the Institute Pasteur’s MLST scheme, but showed ST353 using the Bartual’s MLST scheme and different pulsotypes from the CRAB isolates from 2009 to 2010. In conclusion, this is the first report of emergence and spread of A. baumannii ST191 in Korea, as well of the genetic basis of its antimicrobial resistance.     

Genetic basis of antimicrobial resistance and clonal dynamics of carbapenem-resistant Acinetobacter baumannii sequence type 191 in a Korean hospital

This study investigated the genetic basis of antimicrobial resistance and the epidemiological characteristics of 125 carbapenem-resistant Acinetobacter baumannii (CRAB) isolates collected from 2011 to 2012 in a Korean hospital. All CRAB isolates showed an extensively drug-resistant phenotype, but were susceptible to tigecycline. The bla_OXA − 23 and armA genes were mainly responsible for resistance to carbapenems and aminoglycosides, respectively. Four colistin-resistant CRAB isolates with different pulsotypes were identified. All four colistin-resistant isolates had a deletion at nucleotide 776 in lpxA, while one also had an insertion at nucleotide 732 in lpxA. All CRAB isolates belonged to three sequence types (STs): ST191 (n = 118), ST208 (n = 6), and ST436 (n = 1), but were classified into 33 arbitrary pulsotypes. Of the CRAB ST191 isolates, two main arbitrary pulsotypes 5 (n = 20) and 18 (n = 17) emerged sequentially, but were not clonally related to CRAB isolates collected from 2009 to 2010 in the same hospital. Furthermore, of the two main pulsotypes identified among CRAB ST191 isolates from 2009 to 2010, one was clonally related to sporadic CRAB ST191 isolates from 2011 to 2012, but the other was not related to any CRAB isolate from 2011 to 2012. In conclusion, this study shows the clonal dynamics of CRAB ST191 isolates in a Korean hospital during the last four years.     

医源性肺部感染患者耐碳青霉烯类铜绿假单胞菌及鲍氏不动杆菌的耐药机制分析

目的探讨耐碳青霉烯类铜绿假单胞菌(CRPA)及耐碳青霉烯类鲍氏不动杆菌(CRAB)的耐药机制,为指导临床合理选择抗菌药物提供治疗依据。方法回顾性调查2014年1月-2015年12月医院肺部感染住院患者送检的各类标本中检出病原菌577株,采用改良Hodge方法测定碳青霉烯酶表型,采用B-last方法测定超广谱β-内酰胺酶,分析CRPA及CRAB的耐药性及检出率的相关性。结果铜绿假单胞菌对亚胺培南、美罗培南的耐药率为32.95%和29.55%,而对阿米卡星的耐药率为5.11%,对磺胺甲恶唑/甲氧苄啶100.00%耐药;鲍氏不动杆菌对亚胺培南和美罗培南的耐药率均为47.75%,而对氨曲南100.00%耐药;176株PAE检出CRPA 31株,检出率17.61%,检出耐亚胺培南PAE 17株,检出率54.84%,检出耐美罗培南PAE 14株,检出率45.16%;178株ABA检出CRAB 39株,检出率21.91%,检出耐亚胺培南ABA 22株,检出率56.41%,检出耐美罗培南ABA 17株,检出率43.59%。结论医源性感染患者CRPA及CRAB的耐药率呈逐年增加,临床医师应根据细菌鉴定和药敏结果正确合理使用抗菌药物,以便提高疗效和减少耐药菌株的发生。     

ICU多重耐药鲍曼不动杆菌医院感染暴发流行病学调查

目的调查某院重症监护室（ICU）发生的多重耐药鲍曼不动杆菌医院感染暴发的原因。方法采用前瞻性和回顾性调查相结合的方法,对2012年1月25日-2月10日该院ICU发生的10例下呼吸道感染多重耐药鲍曼不动杆菌患者进行流行病学调查。结果10例患者痰培养分离的鲍曼不动杆菌,除对头孢哌酮/舒巴坦全敏感,左氧氟沙星中度敏感外,对其他16种抗菌药物基本耐药;7例患者经治疗好转后转出ICU,3例死亡。共采集环境标本（未做清洁前）104份,其中从水龙头、治疗车、床头柜、雾化器管道、呼吸机管道和呼吸机操作屏、医务人员手等16份标本分离到鲍曼不动杆菌;16份环境标本分离的鲍曼不动杆菌耐药谱与痰培养菌株一致。经采取综合性控制措施,很好地控制了疫情。结论此次ICU多重耐药鲍曼不动杆菌医院感染暴发流行与医务人员手及医疗环境污染密切相关。     

Nosocomial spread of carbapenem-resistant Acinetobacter baumannii (types ST75 and ST137) carrying blaOXA-23-like gene with an upstream ISAba1 in a Chinese hospital

The most widespread type of carbapenemases among carbapenem-resistant Acinetobacter baumannii (CRAB) belongs to the oxacillinase (OXA) group. A total of 57 CRAB isolates and 20 non-CRAB isolates (i.e., A. baumannii susceptible to carbapenems) were studied to investigate the molecular epidemiology of CRAB isolates and to identify the OXAs responsible for resistance to imipenem. The ISAba1-bla_OXA-23-like gene was detected in all 57 CRAB isolates but was detected in none of the non-CRAB isolates. Pulsed-field gel electrophoresis (PFGE) revealed that clones A and B were the dominant genotypes, and all bla_OXA-23-like gene positive strains were classified as either clone A or B strains. ST75 and ST137 were the most prominent sequence types (STs). Finally, the A. baumannii isolates of clone A, C and F were all demonstrated to be genetically similar to the previously identified European clone II. In conclusion, ST75- and ST137-type CRAB isolates that produced the bla_OXA-23-like gene with an upstream ISAba1 contributed to the nosocomial outbreaks studied in this work.