THE ORIGIN AND SPREAD OF MOSAIC PLASMIDS ENCODING MULTI-DRUG RESISTANCE(Research Supplement to Promote Diversity)

项目摘要/摘要(获奖家长资助金) 许多领先的人类健康组织，如世界卫生组织和疾病中心 美国疾病控制和预防中心(CDC)宣布，增加的细菌病原体是 对多种抗生素的抗药性是一个重大的人类健康危机。这些多重耐药的出现 多药耐药(MDR)病原菌很大程度上是由于通过质粒介导的水平基因转移共享耐药基因。 细菌质粒是一种可移动的遗传元件，可以对多种抗生素产生耐药性，包括 那些被认为是“最后手段的毒品”。我们的长期目标是帮助制定战略 这可以通过洞察共同进化过程来减缓抗生素耐药性的传播 细菌以提高新获得的多药耐药质粒的持久性。新获得的抗性质粒通常 在没有抗生素的情况下不会坚持，但我们和其他人已经证明了细菌中的单一突变 宿主、质粒或两者都能迅速提高这种持久性。我们和其他人也发现了关键的突变 在染色体编码的辅助解旋酶中。因此，细菌中的质粒-解旋酶的相互作用可能是关键 细菌病原体保留新获得的多药耐药质粒的能力。不幸的是，分子 解释这些突变对质粒持久性的积极影响的机制尚不清楚。重要的是 我们还首次表明，这些突变使细菌预先适应了它们所携带的其他多药耐药质粒 在较晚的时间获得，导致它们增强的持久性(称为增加的质粒透过性)。 这表明，具有更高的通透性的细菌可以作为多药耐药的稳定储存库 最终产生具有扩展的抗性基因库的菌株。这种可能性从未出现过 已经测试过了。利用分子技术、实验进化和数学模型，我们提出了 检验以下假设：(I)染色体突变可以使细菌预先适应其他质粒，导致 更大的质粒透过性；(Ii)质粒透过性可以扩大抗生素耐药谱 细菌物种内的特征；以及(Iii)辅助解旋酶与新获得的 广泛分布在多种细菌病原体的多药耐药质粒。这将通过实现以下目标来实现 具体目的：(1)测试(1)宿主/质粒后增加的质粒透过率的一般性 共同进化，以及(Ii)解旋酶突变作为宿主适应新MDR质粒的机制；(2) 确定质粒持久性和渗透性对扩张药物产生的影响 抗性；(3)确定了沙门氏菌引起的质粒成本改进的分子机制。 副解旋酶的突变。如果我们的假设得到数据的支持，稳定一个人的突变 质粒可以改善其他质粒的持久性，并扩大抗性基因库。 同一间牢房。我们的发现将有助于开发新的治疗方法，旨在减缓肺炎的传播。 细菌病原体中的抗生素耐药性。

PROJECT SUMMARY/ABSTRACT (of the Awarded Parent Grant) Many leading human health organizations such as the World Health Organization and the Centers for Disease Control and Prevention (CDC) have declared that the increased prevalence of bacterial pathogens that are resistant to multiple antibiotics is a significant human health crisis. The emergence of these multi-drug resistant (MDR) pathogens is largely due to the sharing of resistance genes by plasmid mediated horizontal gene transfer. Bacterial plasmids are mobile genetic elements that can confer resistance to a variety of antibiotics, including those that are considered to be “drugs of last resort”. Our long-term goal is to aid the development of strategies that can slow the spread of antibiotic resistance by gaining insight into the co-evolutionary processes that allow bacteria to improve the persistence of newly acquired MDR plasmids. Newly acquired resistance plasmids often do not persist in the absence of antibiotics, but we and others have shown that single mutations in the bacterial host, the plasmid, or both can rapidly improve this persistence. We and others also identified critical mutations in chromosomally encoded accessory helicases. Plasmid-helicase interactions in bacteria may therefore be key to the ability of bacterial pathogens to retain newly acquired MDR plasmids. Unfortunately, the molecular mechanisms that explain the positive effects of these mutations on plasmid persistence are unknown. Importantly, we also showed for the first time that these mutations pre-adapt the bacteria to other MDR plasmids that they acquire later in time, leading to their enhanced persistence (referred to as increased plasmid permissiveness). This suggests that bacteria with increased permissiveness can serve as stable repositories for multiple MDR plasmids, eventually generating strains with an expanded arsenal of resistance genes. This possibility has never been tested. Using molecular techniques, experimental evolution and mathematical modeling, we propose to test the following hypotheses: (i) chromosomal mutations can pre-adapt bacteria to other plasmids, leading to greater plasmid permissiveness; (ii) plasmid permissiveness can expand the spectrum of antibiotic resistance traits within a bacterial species; and (iii) accessory helicases are linked to the persistence of newly acquired MDR plasmids across a wide spectrum of bacterial pathogens. This will be done through achieving the following Specific Aims: (1) Test the generality of (i) increased plasmid permissiveness after host/plasmid coevolution, and (ii) helicase mutations as a mechanism of host adaptation to novel MDR plasmids.; (2) determine the effects of plasmid persistence and permissiveness on the emergence of expanded drug resistance; (3) determine the molecular mechanism of plasmid cost amelioration resulting from mutations in accessory helicases. If our hypotheses are supported by our data, mutations that stabilize one plasmid could lead to improved persistence of other plasmids, and expand the arsenal of resistance genes in the same cell. Our findings will aid the development of new therapies aimed at slowing down the spread of antibiotic resistance in bacterial pathogens.