Genetic linkage and cotransfer of a novel, vanB-containing transposon (Tn5382) and a low-affinity penicillin-binding protein 5 gene in a clinical vancomycin-resistant Enterococcus faecium isolate
Genetic linkage and cotransfer of a novel, vanB-containing transposon (Tn5382) and a low-affinity penicillin-binding protein 5 gene in a clinical vancomycin-resistant Enterococcus faecium isolate
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DOI：
10.1128/jb.180.17.4426-4434.1998
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发表时间：
1998-09-01
影响因子：
3.2
通讯作者：
Rice, LB
中科院分区：
文献类型：
--
作者：
Carias, LL;Rudin, SD;Rice, LB
VanB 型万古霉素耐药决定簇的细胞间转移机制以及这些决定簇与高水平氨苄青霉素耐药决定簇几乎普遍相关的机制仍不清楚。我们报告了 Tn5382 的发现，这是一种 ca, 27-kb 推定转座子，编码屎肠球菌中的 VanB 型糖肽抗性。 Tn5382右端内部和vanX(B)二肽酶基因下游的开放阅读框与编码接合转座子Tn916的切除酶和整合酶的基因表现出显着的同源性，Tn5382的末端也与Tn916的末端同源，特别是在与整合酶结合的区域，PCR扩增实验表明Tn5382在大肠杆菌中切除形成环状中间体。粪便。 Tn5382 在屎肠球菌 C68 染色体中的整合发生在 pbp5 基因终止密码子下游 113 bp 处，该基因在该临床分离株中编码高水平的氨苄青霉素耐药性。万古霉素、氨苄西林和四环素耐药性从 C68 转移到粪肠球菌受体菌株的情况在体外以低频率发生，并且与获得包含 Tn5382、pbp5 基因及其推定阻遏基因 psr 的 130 至 160 kb DNA 片段有关。这种大染色体元件的肠球菌间转移似乎是 vanB 操纵子的主要机制这些结果扩展了已知的 Tn916 相关转座子家族，提出了 vanB 操纵子进入肠球菌并在肠球菌中传播的机制，并为临床粪肠球菌菌株中万古霉素和高水平氨苄西林耐药性几乎普遍存在的关联提供了解释。
Mechanisms for the intercellular transfer of VanB-type vancomycin resistance determinants and for the almost universal association of these determinants with those for high-level ampicillin resistance remain poorly defined. We report the discovery of Tn5382, a ca, 27-kb putative transposon encoding VanB-type glycopeptide resistance in Enterococcus faecium. Open reading frames internal to the right end of Tn5382 and downstream of the vanX(B) dipeptidase gene exhibit significant homology to genes encoding the excisase and integrase of conjugative transposon Tn916, The ends of Tn5382 are also homologous to the ends of Tn916, especially in regions bound by the integrase enzyme, PCR amplification experiments indicate that Tn5382 excises to form a circular intermediate in E. faecium. Integration of Tn5382 in the chromosome of E, faecium C68 has occurred 113 bp downstream of the stop codon for the pbp5 gene, which encodes high-level ampicillin resistance in this clinical isolate. Transfer of vancomycin, ampicillin, and tetracycline resistance from C68 to an E, faecium recipient strain occurs at low frequency in vitro and is associated with acquisition of a 130- to 160-kb segment of DNA that contains Tn5382, the pbp5 gene, and its putative repressor gene, psr, The interenterococcal transfer of this large chromosomal element appears to be the primary mechanism for vanB operon spread in northeast Ohio, These results expand the known family of Tn916-related transposons, suggest a mechanism for vanB operon entry into and dissemination among enterococci, and provide an explanation for the nearly universal association of vancomycin and high-level ampicillin resistance in clinical E, faecium strains.