B FRAGILIS MULTIPLE DRUG RESISTANCE--ORGIN AND CONTROL

描述(改编自申请人的摘要)：本建议书是 继续对抗生素耐药机制进行研究 拟杆菌的基因结构、表达和转移。这些 生物体是极地正常植物区系的重要组成部分 并在系统发育上有很大的分歧 从其他常见的人类细菌病原体中分离出来。脆弱类杆菌，在 特别是，是一种有脓肿倾向的重要病原体 队形。 许多β-内酰胺类药物和其他药物已经产生了抗菌素耐药性 用来治疗这些生物。该项目的长期目标是 阐明调控抗生素表达的新机制 这些生物体和系统中的抗药性和毒力 抗性基因的传播。史密斯博士之前的工作确定了 β-内酰胺酶基因CEPA的杂合启动子结构 表达高水平和低水平B-内酰胺酶的菌株，并定义了 常见的表观IS元素就在 抗生素抗性基因启动子。他还克隆并刻画了 拟杆菌属的另外两种β-内酰胺酶基因。并将其描述为 可移动的头孢西丁抗性转座子元件Tn4555的结构， 其Mob区域和其表观ORIT站点，这在配置文件中是必需的 通过共轭转移。Tn4555似乎与以前的 已报告NBU1元素。 目前提案的具体目标是首先确定 抗生素耐药基因表达的激活机制 以脆弱芽孢杆菌CEPA基因为模型。在这一目标下，史密斯博士将 勾画CEPA：：IS1224杂合启动子，对其进行结构分析 IS链接的启动子，并定义了IS1224涉及的机制 换位。在第二个目标下，史密斯博士建议定义 广谱β-内酰胺类药物传播机制的研究 类杆菌的抗药性。为此，他将专注于Tn4555和 对其接合和转位的动员要求。

DESCRIPTION (Adapted from the applicant's abstract): This proposal is a continuation of ongoing studies into the mechanisms of antibiotic-resistance gene structure, expression, and transfer in Bacteroides spp. These organisms are important components of the normal flora of the extremes of the gastrointestinal tract and are substantially phylogenetically diverged from other common human bacterial pathogens. Bacteroides fragilis, in particular, is an important pathogen with a propensity for abscess formation. Antimicrobial resistance has developed to many B-lactams and other drugs used to treat these organisms. The long term goal of the project is to elucidate the novel mechanisms that regulate expression of antibiotic resistance and virulence in these organisms and the systems that contribute to the dissemination of resistance genes. Dr. Smith's prior work identified the hybrid promoter structure of B-lactamase gene, cepA, involving IS1224 in strains expressing high and low levels of B-lactamase and has defined the common occurrence of apparent IS elements just upstream of antibiotic-resistance gene promoters. He has also cloned and characterized two other B-lactamase genes from Bacteroides spp. and characterized the structure of the mobilizable cefoxitin-resistance transposon element Tn4555, its Mob region, and its apparent oriT site, which is required in cis for transfer by conjugation. Tn4555 appears to differ from the previously reported NBU1 element. The specific aims of the current proposal are first to determine the mechanisms activating expression of the antibiotic resistance genes using the B. fragilis cepA gene as a model. Under this aim Dr. Smith will delineate the cepA::IS1224 hybrid promoter, perform structural analysis on IS-linked promoters, and define the mechanisms involved in IS1224 transposition. Under the second aim Dr. Smith proposes to define the mechanisms responsible for the dissemination of broad-spectrum B-lactam resistance in Bacteroides. For this he will focus on Tn4555 and the requirements for its mobilization for conjugation and for its transposition.