高毒力荚膜血清型肺炎克雷伯菌克隆株毒力和耐药性的研究

Report of hypervirulent capsular serotypes of Klebsiella pneumoniae clones groups with enhanced virulence and antimicrobial resistance

目的探讨肺炎克雷伯菌高毒力荚膜血清型的构成以及毒力和耐药性。方法回顾性研究。收集南昌大学第一附属医院2014年1至8月各种临床标本中分离175株肺炎克雷伯菌，从中筛查6种常见高毒力荚膜血清型，并对其展开多位点序列分析，检测其8种毒力基因和17种常见耐药基因，黏液丝试验确定菌株的高黏液性（HM）表型。毒力分数组间比较采用秩和检验，率的组间比较采用）（2检验或Fisher检验。结果175株肺炎克雷伯菌中筛选出高毒力荚膜血清型57株，其中K1、K2、K5、K20、K54和K57型分别占42．1％、31．6％、1．8％、8．8％、3．5％和12．3％，毒力分数（毒力基因个数）的第50百分位数P。分别为7、5、5、5、5．5和7，其中K1型中ST23、ST29菌株的毒力分数为8。K1型的毒力分数与非K1型比较，差异有统计学意义（U=48．500，P〈0．01）。14株（24．6％）ST23均属于Kl荚膜血清型，是最常见的克隆群。有17种药物的耐药率K1型菌株小于非K1型，产超广谱B内酰胺酶（ESBLs）细菌高达42．1％（24／57）。PCR结果显示产SHV型B内酰胺酶30株（占52．6％）、TEM型29株（占50．9％）和CTX—M型27株（占47．4％），测序结果证实均为TEM-1及多种SHV型和CTX—M型。HM阳性率为61．4％（35／57）。另有26．3％（15／57）菌株携带PMQR基因和5．3％（3／57）菌株携带16SrRNA甲基化酶基因。结论高毒力荚膜血清型肺炎克雷伯菌中存在强毒力和（或）强耐药性克隆株，须高度重视，避免广泛流行。

Objective To study the prevalence, virulence and antimicrobial resistance of some hypervirulent capsular serotypes of Klebsiella pneumoniae in the First Affiliated Hospital of Nanchang University. Methods Retrospective study. One hundred and seventy five Klebsiella pneumoniae clinical isolates from all specimens in our hospital from January to August 2014 were collected. All isolates were assessed for six hypervirulent capsular serotypes, sequence type, 8 virulence genes and 17 common antimicrobial resistance genes. Hypermueoviscosity phenotype （HM） of all strains was determined by string test. Virulence scores were compared between groups by Rank-sum test, while the rates of groups were compared by Chi-square test or Fisher exact test. Results Out of 175 strains of Klebsiella pneumoniae, the detection rate of hypervirulent capsular serotypes was 32. 6%. The 57 isolates were divided into capsular serotype K1, K2, K5, K20, K54, and K57, accounting for 42. 1%, 31.6% , 1.8%, 8.8%, 3.5%, and 12. 3%, respectively. The virulence scores （number of virulence genes） Ps0 were 7, 5, 5, 5, 5.5, and7, respectively. ST23 and ST29 isolates belonging to serotype K1 exhibited virulence genes up 8. The virulence scores of serotype K1 were significantly different from that of serotype non-K1 （ U = 48. 500, P 〈 0. 01 ）. Strains of K1-ST23 were the most common isolates, accounting for 24. 6% of the overall isolates. The serotype K1 isolates exhibited lower antimicrobial resistance to 17 kinds of antimicrobials than non-K1 isolates. The positive rate of ESBLs-producing strains was 42. 1% （24/57）. The results of PCR showed that among the 57 strains of hypervirulent capsular serotypes of Klebsiella pneumoniae, 30 were positive for blaSHV （ accounting for 52. 6% ）, 29 positive for blaTEM （ accounting for 50. 9% ）, 27 positive for blaCTX- M （ accounting for 47.4% ）. The sequencing results were as follows ： TEM-1, a variety of CTX-M and SHV. The positive rate of HM was 61.4% （35/57）. In addition, there were 15 strains positive to the PMQR genes and 3 strains positive to the 16S rRNA methylases genes, accounting for 26. 3% （15/57） and 5.3% （3/ 57）, respectively. Conclusion It is important to pay attention to high prevalence of some hypervirulent capsular serotypes of KlebsieUa pneumoniae conal groups with enhanced virulence and （or） antimicrobial resistance in our hospital.