Genetic linkage of the vanB2 gene cluster to Tn5382 in vancomycin-resistant enterococci and characterization of two novel insertion sequences
Genetic linkage of the vanB2 gene cluster to Tn5382 in vancomycin-resistant enterococci and characterization of two novel insertion sequences
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DOI：
10.1099/00221287-146-6-1469
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发表时间：
2000-06-01
期刊：
影响因子：
2.8
通讯作者：
Sundsfjord, A
中科院分区：
文献类型：
--
作者：
Dahl, KH;Lundblad, EW;Sundsfjord, A
vanB型万古霉素耐药是由vanB基因簇编码的，其通过水平基因转移和万古霉素耐药肠球菌（VRE）的克隆传播而传播。vanB基因簇与转座子Tn 5382和插入序列IS 16和IS 256样的遗传连锁先前已被显示。在这项研究中，确定的vanB基因簇亚型，这些元素的连锁进行了检查。vanB 2亚型（n = 14）均显示vanB与Tn 5382共杂交，vanB 1亚型（n = 8）和vanB 3亚型（n = 1）均为Tn 5382阴性。vanB 2基因簇和Tn 5382的接合共转移证明了两个菌株。vanB 2菌株中vanX（B）-ORFC区域的DNA测序证实vanB 2基因簇是Tn 5382的组成部分。未观察到与IS 16和IS 256-like相关的一般连锁模式。在特定的vanB 2亚型毒株中鉴定出两个新的插入序列。(i)在Tn 5382基因的左侧发现了一个1611 bp的元件（ISEnfa 110），其插入位点、末端缺失反向和正向重复序列以及两个保守的基序均符合IS 110家族的结构。(ii)在vanS（B）-vanY（B）基因间区检测到一个787 bp的元件（ISEnfa 200）。它的ORF编码一个与IS 200家族转座酶具有60- 70%同一性的推定蛋白。通过对181株肠球菌分离株进行菌落杂交，未发现ISEnfa 110的进一步拷贝，而在来自美国的另外4株vanB 2菌株中发现了ISEnfa 200。这5个菌株具有相同的ISEnfa 200元件插入位点，Tn 5382位于pbp 5基因的下游，赋予高水平的氨苄青霉素抗性。这些分离株显示出相关的PFGE图谱，表明可能存在VRE菌株的克隆传播，该菌株含有与赋予氨苄青霉素抗性的pbp 5基因相连的Tn 5382-vanB 2-ISEnfa 200元件。
VanB-type vancomycin resistance is encoded by the vanB gene cluster, which disseminates by horizontal gene transfer and clonal spread of vancomycin-resistant enterococci (VRE). Genetic linkage of the vanB gene cluster to transposon Tn5382 and the insertion sequences IS16 and IS256-like has previously been shown. In this study linkage of defined vanB gene cluster subtypes to these elements was examined. All the vanB2 subtype strains studied (n = 14) revealed co-hybridization of vanB and Tn5382, whereas the strains of vanB1 (n = 8) and vanB3 (n = 1) subtypes were Tn5382 negative. Conjugative cotransfer of the vanB2 gene cluster and Tn5382 was demonstrated for two strains. DNA sequencing of the vanX(B)-ORFC region in vanB2 strains confirmed that the vanB2 gene cluster is an integral part of Tn5382. No general pattern of linkage was observed with regard to IS16 and IS256-like. Two novel insertion sequences were identified in specific vanB2 subtype strains. (i) A 1611 bp element (ISEnfa110) was detected in the left flank of Tn5382, Its insertion site, lack of terminal inverted and direct repeats, and two conserved motifs in its putative transposase all conform to the conventions of the IS110 family. (ii) A 787 bp element (ISEnfa200) was detected in the vanS(B)-vanY(B) intergenic region. Its ORF encoded a putative protein with 60-70 % identity to transposases of the IS200 family. No further copies of ISEnfa110 were found by colony hybridization of 181 enterococcal isolates, whereas ISEnfa200 was found in four additional vanB2 strains from the USA. The five strains had identical ISEnfa200 element insertion sites, and Tn5382 was located downstream from a pbp5 gene conferring high-level ampicillin resistance. These isolates showed related PFGE patterns, suggesting possible clonal spread of a VRE strain harbouring a Tn5382-vanB2-ISEnfa200 element linked to a pbp5 gene conferring ampicillin resistance.