Impact of Antibiotics and PBP2a on the Immunopathology of MRSA pneumonia

描述（由申请人提供）：耐甲氧西林金黄色葡萄球菌（MRSA）在世界范围内的快速扩散对公共卫生构成了重大威胁，并且产生的感染已被证明比甲氧西林敏感金黄色葡萄球菌（MSSA）感染更难治疗。其原因尚不清楚，但常见抗生素有效性降低和炎症延长可能导致感染的病理生理，特别是在肺部。虽然MRSA可能对普通抗生素具有耐药性是不言而喻的，但增强或延长炎症的来源可能与细菌的持久性有关，也可能与之无关。金黄色葡萄球菌的细胞壁（像所有革兰氏阳性细菌一样）主要由高度交联的肽聚糖聚合物组成，我们实验室最近的工作表明，吞噬细胞降解金黄色葡萄球菌肽聚糖，通过释放细胞内促炎成分（如细菌DNA），强烈增强炎症反应。金黄色葡萄球菌主动修饰其肽聚糖，使其抗降解并抑制炎症反应，当这种作用被抑制时，金黄色葡萄球菌在体外诱导巨噬细胞产生更多的细胞因子，并在小鼠中引起更多的免疫病理。我们进一步发现，抗生素诱导的金黄色葡萄球菌细胞壁肽聚糖合成的亚致死改变也会导致巨噬细胞引发更强烈的炎症反应。MRSA通过诱导PBP2A(一种肽聚糖合成酶，对？内酰胺抗生素。然而，据报道，PBP2A的表达会导致肽聚糖合成和结构的改变，我们现在已经观察到这直接增强了巨噬细胞的炎症信号传导。基于这些发现，我们得出了一个令人惊讶的假设，即特定的抗生素实际上可能导致MRSA感染期间的免疫病理变得更加明显。我们将用两个目标来检验这个假设。在第一个目标中，我们将直接研究PBP2A和临床通常使用的抗生素对体外金黄色葡萄球菌炎症能力的影响。利用基因敲除小鼠的细胞，我们将确定炎症能力改变的机制。在第二个目标中，我们将转向体内小鼠肺炎模型，以确定抗生素和MRSA表达PBP2A对免疫病理的影响。

DESCRIPTION (provided by applicant): The rapid worldwide proliferation of Methicillin-Resistant S. aureus (MRSA) poses a major threat to public health and produces infections that have proven to be more difficult to treat compared to Methicillin- Susceptible S. aureus (MSSA) infections. The reason for this is unknown, but reduced effectiveness of common antibiotics and prolonged inflammation likely contribute to the pathophysiology of infection, especially in the lung. While it is self-evident that MRSA may be resistant to common antibiotics, the source of enhanced or prolonged inflammation may or may not be related to perseverance of the bacteria. The cell wall of S. aureus (like all Gram-positive bacteria) is made up primarily of highly cross-linked peptidoglycan polymer, and recent work from our labs has suggested that degradation of the S. aureus peptidoglycan by phagocytes strongly enhances inflammatory responses by releasing pro-inflammatory intracellular components such as bacterial DNA. S. aureus actively modifies its peptidoglycan to make it resistant to degradation and suppresses inflammatory responses, and when this effect is inhibited, S. aureus induces greater cytokine production from macrophages in vitro and causes more immunopathology in mice. We have further found that sub-lethal alterations in cell wall peptidoglycan synthesis induced by antibiotics in S. aureus als causes macrophages to elicit a more powerful inflammatory response. MRSA becomes antibiotic-resistant through induced expression of PBP2A, a peptidoglycan synthesizing enzyme that is resistant to ?-lactam antibiotics. Expression of PBP2A, however, has been reported to cause alterations in peptidoglycan synthesis and structure, and we have now observed that this directly enhances inflammatory signaling in macrophages. Based on these findings, we come to the surprising hypothesis that specific antibiotics may actually cause immunopathology to become more pronounced during MRSA infection. We will test this hypothesis in two aims. In the first aim, we will examine directly the effects of PBP2A and antibiotics typically used in the clinic on the inflammatory capacity of S. aureus in vitro. Using cells from knockout mice we will identify the mechanisms underlying alterations in inflammatory capacity. In the second aim, we will move to in vivo mouse pneumonia models to determine the effects of antibiotics and PBP2A expression by MRSA on immunopathology.