Acquired bacitracin resistance in Enterococcus faecalis is mediated by an ABC transporter and a novel regulatory protein, BcrR
Acquired bacitracin resistance in Enterococcus faecalis is mediated by an ABC transporter and a novel regulatory protein, BcrR
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DOI：
10.1128/aac.48.10.3743-3748.2004
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发表时间：
2004-10-01
影响因子：
4.9
通讯作者：
Cook, GM
中科院分区：
文献类型：
--
作者：
Manson, JM;Keis, S;Cook, GM
杆菌肽耐药性（杆菌肽MIC，大于或等于256 μ g ml（-1））已在粪肠球菌中报道，在本研究中，我们报道了这种耐药性的遗传基础。用转座子Tn 917进行诱变，选择E.对杆菌肽抗性降低的粪肠杆菌突变体。获得了两个杆菌肽敏感突变体（MIC，32 μ g ml（-1）），并将Tn 917插入定位于指定为bcrA和bcrB的基因。BcrA（ATP结合结构域）和BrcB（跨膜结构域）的氨基酸序列被预测构成同源二聚体ATP结合盒（ABC）转运蛋白，其功能是大肠杆菌杆菌对杆菌肽耐药所必需的。粪便。bcrA和bcrB基因与第三个基因bcrD组成一个操纵子，bcrD与十一肾上腺素激酶具有同源性。北方分析表明，bcrA、bcrB和bcrD被转录为多顺反子信息，其由增加浓度的杆菌肽诱导，而不是由其它细胞壁活性抗微生物剂（例如，万古霉素）。bcrABD操纵子的上游是一个假定的调控基因bcrR。bcrR基因组成型表达，bcrR的缺失导致杆菌肽敏感表型。在bcrR突变体中没有观察到bcrABD表达，表明BcrR是杆菌肽抗性所必需的基因的激活剂（即，bcrABD）。杆菌肽耐药基因定位于质粒上，该质粒以较高的频率转移到大肠杆菌中。粪肠球菌菌株JH 2 -2。本报告首次描述了大肠杆菌获得性杆菌肽耐药所必需的基因。粪便。
Bacitracin resistance (bacitracin MIC, greater than or equal to256 mug ml(-1)) has been reported in Enterococcus faecalis, and in the present study we report on the genetic basis for this resistance. Mutagenesis was carried out with transposon Tn917 to select for E. faecalis mutants with decreased resistance to bacitracin. Two bacitracin-sensitive mutants (MICs, 32 mug ml(-1)) were obtained and Tn917 insertions were mapped to genes designated bcrA and bcrB. The amino acid sequences of BcrA (ATP-binding domain) and BrcB (membrane-spanning domain) are predicted to constitute a homodimeric ATP-binding cassette (ABC) transporter, the function of which is essential for bacitracin resistance in E. faecalis. The bcrA and bcrB genes were organized in an operon with a third gene, bcrD, that had homology to undecaprenol kinases. Northern analysis demonstrated that bcrA, bcrB, and bcrD were transcribed as a polycistronic message that was induced by increasing concentrations of bacitracin but not by other cell wall-active antimicrobials (e.g., vancomycin). Upstream of the bcrABD operon was a putative regulatory gene, bcrR. The bcrR gene was expressed constitutively, and deletion of bcrR resulted in a bacitracin-sensitive phenotype. No bcrABD expression was observed in a bcrR mutant, suggesting that BcrR is an activator of genes essential for bacitracin resistance (i.e., bcrABD). The bacitracin resistance genes were found to be located on a plasmid that transferred at a high frequency to E. faecalis strain JH2-2. This report represents the first description of genes that are essential for acquired bacitracin resistance in E. faecalis.