临床分离碳青霉烯类耐药与非耐药肺炎克雷伯菌株的血清荚膜类型特征及毒力基因分布研究

Characteristics of capsular serotypes and virulence genes in clinical isolates of carbapenem-resistant and non-carbapenem-resistant Klebsiella pneumoniae strains

目的分析碳青霉烯类耐药肺炎克雷伯菌(CRKP)和碳青霉烯类非耐药肺炎克雷伯菌(non-CR KP)的荚膜血清型和携带毒力基因的情况。方法选取医院临床微生物室2015年3月-10月保留的各种临床标本分离出的79株肺炎克雷伯菌,采用改良Hodge试验进行耐药表型筛查,黏液丝试验确定菌株的高黏液(HM)表型,采用PCR和基因测序检测耐药基因、荚膜血清型及毒力基因,通过ERIC-PCR分析菌株间的同源性。结果从所有样本中分离到CRKP31株,non-CR KP 48株,改良Hodge阳性21株,HM表型阳性率为16.5%(13/79),其中5株为CRKP,荚膜血清型以K1型为主;荚膜血清型中以K1、K2型为主,K5、K20、K54和K57阳性率较低,各只检测出一株;CRKP中检测到有一株携带KPC耐药基因的K1型肺炎克雷伯菌;毒力基因rmpA,aerobactin和iroN三者分布具有高度一致性,且在CRKP和non-CR KP肺炎克雷伯菌中的检出率差异明显(P<0.05);毒力分数柱状图和ERIC-PCR图谱分别显示CRKP呈明显集中趋势,菌株间同源性高,而non-CR KP呈离散趋势,无明显同源性。结论 CRKP在携带毒力基因和高毒力荚膜血清型阳性率上比non-CR KP低;CRKP间以克隆为主要传播方式,non-CR KP间以非克隆为主要传播方式。

OBJECTIVE To observe the capsular serotypes and virulence genes in carbapenem-resistant Klebsiella pneumoniae（CRKP）and non-carbapenem-resistant K.pneumoniae（non-CRKP）strains.METHODS A total of 79 strains of K.pneumoniae were isolated from various clinical specimens that were reserved in clinical microbiology lab from Mar 2015 to Oct 2015,the drug resistance phenotypes were screened by using modified Hodge test,the phenotypes of hypermucoviscosity（HM）of the strains were determined through slime test,the drug resistance genes,capsular serotypes and virulence genes were detected by means of PCR and gene sequencing,and the homology among the strains was analyzed with the use of ERIC-PCR.RESULTS Totally 31 strains of CRKP and 48 strains of non-CRKP were isolated from the specimens,21 strains showed positive for the modified Hodge test,the positive rate of HM phenotype was 16.5%（13/79）,5 of which were CRKP,and the capsular serotype K1 wad dominant.The K1 and K2 were dominant among the capsular serotypes,the positive rates of K5,K20,K54 and K57 were low,only 1 strain of each serotype was detected.Among the CRKP strains,1 strain of K1-type K.pneumoniae was detected to carry with drug resistance gene KPC;the distribution of the virulence genes rmpA,aerobactin and iroN was highly consistent,and there were significant differences in the detection rates between the CRKP and non-CRKP strains（P〈0.05）.The histogram of virulence score and ERIC-PCR atlas demonstrated that the CRKP strains showed a notable concentrating trend and high homology,on the contrary,the non-CRKP strains showed a discrete trend and did not show remarkable homology.CONCLUSION The positive rates of virulence genes and highly virulent capsular serotypes are lower in the CRKP strains than in the nonCRKP strains.The cloning is the major spread approach of the CRKP strains,while the non-cloning is the major spread approach of the non-CRKP strains.