DISSEMINATION OF MACROLIDE RESISTANCE ELEMENTS IN STREPTOCOCCUS PNEUMONIAE

肺炎链球菌中大环内酯类耐药元件的传播

• 批准号: 10027021
• 负责人: DAVID S STEPHENS
• 金额: $ 15.74万
• 依托单位: UNIVERSITY OF MISSISSIPPI MED CTR
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-03-06 至 2021-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10027021
• 关键词: DISSEMINATION; MACROLIDE; RESISTANCE; ELEMENTS; STREPTOCOCCUS

Abstract Streptococcus pneumoniae (Spn) colonizes the epithelial surface of the human nasopharynx in early childhood and remains a significant cause of respiratory illness. Globally, Spn causes 15 million cases of pneumococcal disease (PD) each year leading to approximately ∼0.5 million deaths in children. Treatment of PD has been hindered by emergence of antimicrobial resistance, including the resistance to macrolides. Most pneumococcal macrolide resistance is conferred by Erm(B), the RNA methylase, and/or efflux/ribosomal protection mediated by Mef(E)/Mel on the macrolide efflux genetic assembly (Mega) element. The Mega element, related to Tn916 conjugative transposons but does not encode putative recombinases, has integrated into at least four loci in the pneumococcal chromosome, Mega classes I–IV. Molecular epidemiological studies demonstrated a higher prevalence of isolates containing the class II Mega, which is not caused by clonal expansion. Moreover, a wide array of complex Tn916 related mobile genetic elements, termed integrative and conjugative elements (ICEs), has emerged that also facilitate dissemination of macrolide resistance (both ermB and Mega) and additional antibiotic resistance markers. While acquisition of Mega and ICE-encoded resistance presumably occurs during colonization of the human nasopharynx, the efficiency and the specific mechanisms by which Mega elements and ICEs spread among pneumococci in the nasopharynx is not well understood. Our novel discovery of pneumococcal unidirectional transformation in the human nasopharyngeal biofilms has provided new insights on gene transfer in S. pneumoniae. In this proposal, using an established model of human nasopharyngeal consortial biofilms and the newly characterized uni-directional gene transfer phenomenon, we will determine the mechanisms and frequencies of macrolide resistance dissemination mediated by the Mega elements and ICEs. In Aim 1 we will evaluate whether genomic recombination hot spots or strain background, influence the recombination frequency (rF) and account for different prevalence among Mega classes. Donor strains engineered with each of the four Mega classes and defined pneumococcal clinical isolates containing the Mega classes will be conducted to assess the contribution of genomic loci and strain backgrounds, respectively. Both the rF and the specific recombination sites will be defined in recombinants. In aim 2 we will investigate whether conjugation or recombination via transformation, drives the mobilization of ICE- encoded macrolide resistant determinants. The molecular mechanism of ICE-dissemination among pneumococci will be further investigated using mutants with inactivated transposon-encoded mobilization proteins and proteins mediating competence. Identifying the horizontal dissemination mechanisms and frequencies of the two-major macrolide resistance genetic determinants will be valuable for new interventions aimed at decreasing the burden of antibiotic resistance dissemination in S. pneumoniae.

摘要 肺炎链球菌（Spn）在人鼻咽上皮表面定植， 幼儿期，仍然是呼吸道疾病的一个重要原因。在全球范围内，Spn导致1500万例 肺炎球菌疾病（PD）每年导致约1050万儿童死亡。人们对PD 已经被抗微生物剂耐药性的出现所阻碍，包括对大环内酯类的耐药性。最 肺炎球菌的大环内酯耐药性是由Erm（B）、RNA甲基化酶和/或外排/核糖体 由Mef（E）/Mel介导的对大环内酯外排遗传组装（Mega）元件的保护。巨型 元件，与Tn 916接合转座子相关，但不编码推定的重组酶，已整合 肺炎球菌染色体上至少有四个位点，Mega Class I-IV。分子流行病学研究 证明了含有II类Mega的分离株的患病率较高，这不是由克隆引起的。 扩张.此外，一系列复杂的Tn 916相关的移动的遗传元件，称为整合的和 接合元件（ICE）的出现，也促进了大环内酯类耐药的传播（ermB 和Mega）和另外的抗生素抗性标记物。虽然获得了Mega和ICE编码的抗性， 推测发生在人鼻咽定植期间、效率和具体机制 Mega元素和ICE在鼻咽肺炎球菌中传播的机制尚不清楚。我们 在人鼻咽生物膜中发现了肺炎球菌单向转化的新发现， 为S.肺炎。在本建议中，使用已建立的 人鼻咽部聚生生物膜和新表征的单向基因转移 现象，我们将确定大环内酯类耐药传播的机制和频率 由Mega元素和ICE介导。在目标1中，我们将评估基因组重组热点是否 或菌株背景，影响重组频率（rF），并解释不同的患病率之间 超级课程用四种Mega分类中的每一种进行工程改造的供体菌株和定义的肺炎球菌临床 将进行含有Mega类的分离物，以评估基因组位点和菌株的贡献。 背景，分别。rF和特异性重组位点都将在重组体中定义。在 目的2我们将研究是否通过转化的接合或重组，驱动ICE的动员， 编码的大环内酯类耐药决定簇。ICE传播的分子机制 将使用具有失活转座子编码的动员的突变体进一步研究肺炎球菌 蛋白质和蛋白质介导的能力。确定横向传播机制， 两个主要的大环内酯类耐药遗传决定因素的频率对于新的干预措施将是有价值的 目的是减少S.肺炎。