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

Study on carbapenemase genotypes in carbapenem-resistant Acinetobacter baumannii and insertion sequence ISAba1

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。

OBJECTIVE To investigate the clinical distribution and antibiotic resistance of carbapenem-resistant Acinetobacter baumannii and explore the relationship between the insertion sequence ISAba1and the antibiotic resistance.METHODS A total of 270strains of carbapenem-resistant A.baumannii were collected,then the drug susceptibility testing was performed by using K-B method,the carbapenemases were detected by means of modified Hodge test,the metalloenzymes were detected with the use of double-disk synergy test;the OXA-51,OXA-23,OXA-58,OXA-24,IMP,VIM,and SIM were tested by using multiplex PCR,the ISAbal-OXA-23gene and ISAbal-OXA-51gene were detected and sequenced with the use of PCR,and the result of the drug susceptibility testing for the strains was statistically analyzed by using WHONET 5.6software.RESULTS Of the 18antibiotics tested,the drug resistance rates to 14antibiotics exceeded 90.0%;the drug resistance rate to piperacillin was the highest（100.0%）,cefoperazone-sulbactam the lowest（48.9%）.The modified Hodge test showed that the carbapenemases were tested positive in 156strains with the positive rate of 57.8%;the metalloenzymes were tested negative in all the strains.The OXA-51gene has been detected in all the 270strains,the OXA-23gene in 267 strains,the OXA-58gene in 1strain;however,the OXA-24,IMP,VIM,or SIM have not been detected.The insertion sequence ISAbal has been detected in the upstream of OXA-23gene in 267strains but has not been detected in the upstream of any OXA-51.CONCLUSION The carbapenem-resistant A.baumannii strains show severe drug resistance.The OXA-51gene and the OXA-23gene are the predominant carbapenemase genotypes in the A.baumannii strains isolated in the area.The insertion sequence ISAba1is commonly seen in the upstream of the OXA-23gene.The ISAbal-OXA-23is the important mechanism for the drug resistance of A.baumannii to carbapenem.