福建宋内志贺菌临床分离株MLVA分型的初步研究

Preliminary study on MLVA classification of Shigella sonnei clinical isolates in Fujian Province

目的评价多位点可变数目串联重复序列分析(multiple-locus variable-number tandem-repeat analysis,MLVA)对福建地区宋内志贺菌的分型能力,为了解宋内志贺菌分子流行病学特征及疫情暴发时病原的溯源提供分析方法和基础数据。方法选择8个VNTR(Variable Number of Tandem Repeats)位点对68株临床分离株宋内志贺菌进行PCR扩增和毛细管电泳,利用BioNumerics软件进行聚类分析并构建最小生成树(Minimum spanning tree,MST),结合流行病学资料分析分型结果。结果 68株宋内志贺菌经MLVA分型后遗传关联度在20.647%~100%之间,按照100%的相似水平可分为66个MLVA型,呈遗传多态性,分辨系数为0.9986;有6个优势基因群(G1~G6),表现出时间地区聚集性。在最小生成树中,芗城分离株显示不同程度的亲缘关系,形成本土流行的优势克隆群;新罗分离株来源分散,存在少数优势基因簇。结论福建临床分离株宋内志贺菌具有基因多态性,MLVA方法对该菌有较好的分型能力,可用于研究菌株间的亲缘关系。

Objective To evaluate the ability of multiple-locus variable-number tandem-repeat analysis (MLVA)to classify S.sonnei from Fujian Province in order to provide evidence with which to determine the epidemiological characteristics of dysentery and to trace its origin in the event of an outbreak.Methods Eight variable number of tandem repeats (VNTR)loci from the 68 strains of S.sonnei were amplified with PCR and subjected to capillary electrophoresis.The software BioNumerics (Version 6.6)was used to perform cluster analysis and construct a minimum spanning tree (MST),the results of which were analyzed on the basis of epidemiological data.Results The 8 loci had different poIymorphisms that were more frequent in loci SS1,SS3,and SS6 but less frequent in loci SS10 and SS23.Isolates were dif- ferentiated into 66 MLVA types,the similarity coefficient of which was 20.647 to 100% with a D index of 0.9986 and no dominant type.However,there were 6dominant clusters (G1-G6) with some degree of temporal and spatial clustering, such as G3,G5,and G6.G3 and G4 included a Iarger proportion of MLVA types,with respective proportions of 25% and 14.71%.The minimum spanning tree had 2branches,one emanating from MT 13 and the other from MT 22.Strains from the Xiangcheng District displayed a genetic relationship to different degrees and they formed a dominant clonal complex endemic to the area.Strains from the Xinluo District originated from disparate sources and harbored several dominant gene clusters.Conclusion Clinical isolates from Fujian had genotypes for various polymorphisms with regional and temporal clustering,and MLVA was able to type S.sonnei.These findings can be used to study the genetic relationship among strains.