β-Lactam Resistance in Methicillin-Resistant Staphylococcus aureus USA300 Is Increased by Inactivation of the ClpXP Protease
β-Lactam Resistance in Methicillin-Resistant Staphylococcus aureus USA300 Is Increased by Inactivation of the ClpXP Protease
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DOI：
10.1128/aac.02802-14
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发表时间：
2014-08-01
影响因子：
4.9
通讯作者：
Frees, Dorte
中科院分区：
文献类型：
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作者：
Baek, Kristoffer T.;Grundling, Angelika;Frees, Dorte
耐甲氧西林金黄色葡萄球菌（MRSA）获得了编码肽聚糖转肽酶、青霉素结合蛋白2a （PBP2a）的mecA基因，该基因对β -内酰胺的亲和力降低。快速传播和高毒力的社区获得性（CA） MRSA菌株最近成为没有接触卫生保健系统的个人感染的常见原因。在这项研究中，我们发现ClpXP蛋白酶组分的失活大大增加了CA-MRSA USA300菌株的β -内酰胺抗性水平，这表明ClpXP的蛋白水解活性控制着调节β -内酰胺抗性的一种或多种途径。这些途径不涉及控制mecA的表达，因为在clp突变体中PBP2a的细胞水平没有改变。对clpX和clpP突变体细胞包膜特性的分析揭示了许多不同的表型，这些表型可能有助于增强β -内酰胺耐受性。与野生型相比，两种突变体的细胞壁都明显变厚，肽聚糖交联增加，单体多肽种类的组成也发生了变化。此外，在clp突变体中观察到sle1介导的肽聚糖水解的变化和主要自溶素Atl加工的改变。总之，本文的结果指出了ClpXP蛋白酶在控制细胞壁代谢中的重要作用，并为决定菌株依赖性β -内酰胺耐药性的分子因素提供了新的见解。
Methicillin-resistant Staphylococcus aureus (MRSA) has acquired the mecA gene encoding a peptidoglycan transpeptidase, penicillin binding protein 2a (PBP2a), which has decreased affinity for beta-lactams. Quickly spreading and highly virulent community-acquired (CA) MRSA strains recently emerged as a frequent cause of infection in individuals without exposure to the health care system. In this study, we found that the inactivation of the components of the ClpXP protease substantially increased the beta-lactam resistance level of a CA-MRSA USA300 strain, suggesting that the proteolytic activity of ClpXP controls one or more pathways modulating beta-lactam resistance. These pathways do not involve the control of mecA expression, as the cellular levels of PBP2a were unaltered in the clp mutants. An analysis of the cell envelope properties of the clpX and clpP mutants revealed a number of distinct phenotypes that may contribute to the enhanced beta-lactam tolerance. Both mutants displayed significantly thicker cell walls, increased peptidoglycan cross-linking, and altered composition of monomeric muropeptide species compared to those of the wild types. Moreover, changes in Sle1-mediated peptidoglycan hydrolysis and altered processing of the major autolysin Atl were observed in the clp mutants. In conclusion, the results presented here point to an important role for the ClpXP protease in controlling cell wall metabolism and add novel insights into the molecular factors that determine strain-dependent beta-lactam resistance.