B FRAGILIS MULTIPLE DRUG RESISTANCE--ORGIN AND CONTROL

描述（改编自申请人的摘要）：本提案是一项 继续进行对抗药性机制的研究 拟杆菌属的基因结构、表达和转移 这些 生物体是极端环境中正常植物群的重要组成部分， 胃肠道，并且基本上在遗传学上是分叉的 其他常见的人类细菌病原体。 脆弱拟杆菌， 特别是，是一种重要的病原体，具有脓肿倾向 阵 抗生素耐药性已发展到许多β-内酰胺类和其他药物 用于治疗这些生物体。 该项目的长期目标是 阐明调控抗生素表达的新机制 这些生物体的抗性和毒力，以及 抵抗基因的传播。 史密斯博士之前的研究发现 β-内酰胺酶基因cepA的杂合启动子结构，涉及IS 1224， 表达高水平和低水平B-内酰胺酶的菌株，并已定义了 常见的明显的IS元素就在 抗病基因启动子。 他还克隆了 两种来自拟杆菌属的其他β-内酰胺酶基因。 并表征心肠 可移动的头孢西丁抗性转座子元件Tn 4555的结构， 它的Mob区域和它的表观oriT位点，这是顺式形成所必需的。 通过接合转移。 Tn 4555似乎与以前不同 NBU 1元素。 本提案的具体目标是首先确定 激活抗生素抗性基因表达的机制， B。fragilis cepA基因作为模型。 在这一目标下，史密斯博士将 描述cepA：：IS 1224杂合启动子，对cepA：：IS 1224杂合启动子进行结构分析， IS-连接的启动子，并定义了参与IS 1224的机制 换位 在第二个目标下，史密斯博士建议定义 广谱β-内酰胺传播的机制 拟杆菌属的耐药性。 为此，他将重点放在Tn 4555和 需要其移动以用于缀合和其转座。

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.