Cloning of the Staphylococcus aureus ddh gene encoding NAD(+)-dependent D-lactate dehydrogenase and insertional inactivation in a glycopeptide-resistant isolate
Cloning of the Staphylococcus aureus ddh gene encoding NAD(+)-dependent D-lactate dehydrogenase and insertional inactivation in a glycopeptide-resistant isolate
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DOI：
10.1128/jb.179.21.6756-6763.1997
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发表时间：
1997-11-01
影响因子：
3.2
通讯作者：
Daum, RS
中科院分区：
文献类型：
--
作者：
BoyleVavra, S;deJonge, BLM;Daum, RS
葡萄球菌中低水平糖肽耐药的机制尚不清楚。Ddh（W. M. Milewski，S. Boyle-Vavra，B.莫雷拉角C. Ebert和R. S. Daum，Antimicrob.探员凯莫特。40：166-172，1996）和含有编码Ddh的ddh基因的RNA转录物，与易感亲本分离物523相比，在万古霉素抗性分离物523 k中以增加的量存在。序列分析表明Ddh与NAD（+）依赖的D-乳酸脱氢酶（D-nLDH）和VanH有关。后一种蛋白质通过合成对万古霉素具有低亲和力的D-乳酸终止肽聚糖前体生物合成所需的D-乳酸，对屎肠球菌和粪肠球菌中的高水平糖肽抗性至关重要。我们现在提供了ddh基因产物是金黄色葡萄球菌D-nLDH的直接证据，以下将该蛋白质称为D-nLDH。然而，这种蛋白在分离物523 k中的过量产生并不导致含有D-乳酸的肽聚糖前体的产生，并且523 k的ddh突变体的敏感性测试表明S.金黄色葡萄球菌D-nLDH不是该分离株糖肽抗性所必需的。我们的结论是糖肽耐药的机制，在这个分离株是不同的肠球菌。
The mechanism of low-level glycopeptide resistance among staphylococci is not known. A cytoplasmic protein, provisionally called Ddh (W. M. Milewski, S. Boyle-Vavra, B. Moreira, C. C. Ebert, and R. S. Daum, Antimicrob. Agents Chemother. 40:166-172, 1996), and the RNA transcript that contains the ddh gene, which encodes Ddh, are present in increased amounts in a vancomycin-resistant isolate, 523k, compared with the susceptible parent isolate, 523. Sequence analysis had previously revealed that Ddh is related to NAD(+)-dependent D-lactate dehydrogenase (D-nLDH) and VanH. This latter protein is essential for high-level glycopeptide resistance in Enterococcus faecium and Enterococcus faecalis by synthesizing the D-lactate needed for biosynthesis of D-lactate-terminating peptidoglycan precursors with low affinity for vancomycin. We now provide the direct evidence that the ddh gene product is Staphylococcus aureus D-nLDH and hereafter refer to the protein as D-nLDH. However, overproduction of this protein in isolate 523k did not result in production of D-lactate-containing peptidoglycan precursors, and susceptibility testing of ddh mutants of 523k demonstrated that S. aureus D-nLDH is not necessary for glycopeptide resistance in this isolate. We conclude that the mechanism of glycopeptide resistance in this isolate is distinct from that in enterococci.