Molecular basis of decreased susceptibility to beta-lactam antibiotics in Streptococcus pyogenes

标题：β-内酰胺类抗生素敏感性降低的分子基础 酿脓链球菌 项目摘要/总结 人类细菌病原体化脓性链球菌（A组链球菌，GAS）引起超过 全世界每年有7亿人感染。β-内酰胺类抗生素是，而且一直是， 治疗GAS咽炎和侵袭性感染。原因仍然笼罩在神秘之中， 据推测，这种病原体70年来一直对β-内酰胺抗生素敏感。 然而，最近的一篇论文描述了两种引起GAS感染的菌株， 对β-内酰胺类抗生素氨苄青霉素和阿莫西林敏感，在美国引起极大关注 国家和国际传染病界。这一发现，加上我们最近的发现， 对β-内酰胺类抗生素敏感性显著降低的侵袭性GAS菌株 比以前认为的更普遍和地理上更广泛，已经成为催化剂， 在此提出的研究。为了实现我们的目标， 在特定基因突变和GAS β-内酰胺敏感性降低之间， 提出了目标。具体目标1：测序和分析> 11，000株菌株的基因组，以确定 青霉素结合蛋白2X（pbp 2x）和青霉素结合蛋白1A中存在的突变谱 （pbp 1A）基因在从咽炎和无症状携带者回收的GAS中的表达。我们将确定9个 常用的β-内酰胺类抗生素对2,750株（25%）菌株的作用。已知这两个基因的突变 降低许多生物体（包括致病性链球菌）对β-内酰胺的敏感性。我们将利用我们的 数十年来从全球来源回收的40，000种GAS菌株的独特集合。具体目标二： 构建并分析50个同基因突变菌株，以验证特定天然存在的 PBP 2X和PBP 1A中的氨基酸替换降低了GAS对β-内酰胺的敏感性 抗生素，如通过MIC敏感性分析判断的。这两个目标中提出的研究结果 将提供必要的广泛的独特数据，以更充分地了解这一关键的新的范围， 抗菌素耐药性威胁。有理由推测，由此产生的数据也可能最终导致 新的翻译策略，以预防，限制和治疗耐药GAS感染。的主要动机 是在很短的时间内生成并提供这些广泛的分子数据， 对研究、医疗和公共卫生界的最大利用。我们认为， 研究应该在二十年前完成，在人们认识到我们在这方面存在巨大差距之后不久， 我们关于GAS如何降低对β-内酰胺类抗生素敏感性的知识。首先是 拟议的研究将产生一个社区数据资源，可以挖掘和使用的所有个人 从不同的重点领域研究GAS感染和抗菌素耐药性。

DESCRIPTIVE TITLE: Molecular basis of decreased susceptibility to beta-lactam antibiotics in Streptococcus pyogenes PROJECT ABSTRACT/SUMMARY The human bacterial pathogen Streptococcus pyogenes (group A streptococcus, GAS) causes more than 700 million human infections annually worldwide. Beta-lactam antibiotics are, and have been, the first-line treatment for GAS pharyngitis and invasive infections. For reasons that remain shrouded in mystery and speculation, this pathogen has continued to be uniformly susceptible to beta-lactam antibiotics for 70 years. However, a recent paper described two GAS infection-causing strains with significantly decreased susceptibility to the beta-lactam antibiotics ampicillin and amoxicillin, causing great concern in the United States and international infectious disease community. This revelation, coupled with our recent discovery that invasive GAS strains with significantly decreased susceptibility to beta-lactam antibiotics are far more common and geographically widespread than previously thought, have served as the catalyst for the research proposed herein. To achieve our goal of greatly enhancing current understanding of the relationship between specific gene mutations and decreased GAS beta-lactam susceptibility, the following two specific aims are proposed. Specific Aim 1: Sequence and analyze the genomes of >11,000 strains to define the spectrum of mutations present in the penicillin-binding protein 2X (pbp2x) and penicillin-binding protein 1A (pbp1A) genes in GAS recovered from pharyngitis and asymptomatic carriers. We will determine MICs for nine commonly used beta-lactams on 2,750 (25%) of the strains. Mutations in these two genes are known to confer decreased beta-lactam susceptibility in many organisms, including pathogenic streptococci. We will exploit our unique collection of 40,000 GAS strains recovered over decades from global sources. Specific Aim 2: Construct and analyze 50 isogenic mutant strains to test the hypothesis that specific naturally-occurring amino acid replacements in PBP2X and PBP1A decrease the susceptibility of GAS to beta-lactam antibiotics, as judged by MIC susceptibility analysis. The results of the studies proposed in these two aims will provide extensive unique data necessary to more fully understand the scope of this critical new antimicrobial resistance threat. It is reasonable to speculate that the resulting data may also ultimately lead to novel translational strategies to prevent, limit, and treat antibiotic-resistant GAS infections. A key motivation is to generate and make available this extensive molecular data in a very short timeframe so that it can be of the greatest use to the research, medical, and public health communities. We believe much of the proposed research should have been done two decades ago, soon after it was recognized that we had massive gaps in our knowledge about how GAS develops decreased susceptibility to beta-lactam antibiotics. Foremost, the proposed research will generate a community data resource that can be mined and used by all individuals studying GAS infections and antimicrobial resistance from different areas of emphasis.