Relationships Among Metronidazole Resistance, Pharmacodynamics and Treatment Outcomes in Clostridium difficile Infection

项目摘要/摘要 艰难梭菌是抗生素相关性腹泻的主要原因。自2003年以来，其发病率和严重程度 艰难梭菌感染(CDI)的发病率在美国和全球都有所上升。2011年，美国约有29,000人死亡 从50万起CDI案件中脱颖而出。2013年，疾控中心将艰难梭菌列为紧急威胁。这些趋势是 与出现流行毒株有关，特别是027疫情。流行病027导致了大约三分之一的 美国的CDI，并有导致严重疾病的趋势。一线药物甲硝唑现在更多 与30年前相比，今天更容易失败。我们的研究表明，到目前为止，甲硝唑耐药性是一种 导致治疗失败的被忽视的因素。这项提议试图了解抵抗的影响 甲硝唑治疗反应及甲硝唑耐药(MTZ-R)的遗传基础研究 艰难抉择。我们发现，流行株027的一部分对甲硝唑的敏感性降低， 当在新鲜的亚铁血红素中测试时。利用新鲜的血红素，我们鉴定了其他对甲硝唑耐药的流行菌株。 来自不同的血统。血红素诱导甲硝唑耐药性的表达，否则不会 检测到。我们证明了抗药性发生在动物的治疗过程中，它可以在实验室中进行选择- 媒体。这项工作对公共卫生保健具有重大意义，因为甲硝唑的影响 抗药性没有得到很好的描述。我们的研究将为耐药性如何影响治疗提供见解。 对甲硝唑的反应，并将揭示它在027流行病和其他谱系中的进化过程。目标1.目标 描述MTZ-R的临床影响。它使用病人粪便的生物库来评估殖民 耐药菌株、正在治疗的耐药性上升以及是否阻碍了对MTZ的反应。进一步的验证是 在临床反映CDI的体外和动物模型中完成。目的2.测试低水平的结肠素 MTZ促进了MTZ-R的继续治疗发展，如果它对MTZ-R菌株的CDI无效。MTZ 将其与未吸收的MTZ类似物进行比较，以量化MTZ-R在低剂量和高剂量药物中的出现 CDI动物体内的水平。未被吸收的MTZ类似物也将测试高药物水平在 因耐药菌株而导致的CDI分解为冒号。目的3.阐明MTZ-R的实验室进化 和病人的分离株。这一目的使艰难梭菌领域向前推进，将表型与其耐药性联系起来。 基因分型并阐明了甲硝唑耐药性在三个环境中的进化基础：实验室-媒体， 动物模型和患者的临床分离株。然后，它应用计算基因组学和分子生物学 识别和验证抗药性的汇聚或发散路径的实验。公共卫生。这个

PROJECT SUMMARY/ABSTRACT Clostridium difficile is the main cause of antibiotic-associated diarrhea. Since 2003, the incidence and severity of C. difficile infection (CDI) has risen in the U.S. and globally. In the U.S. in 2011, there were ~29,000 deaths from ~500,000 CDI cases. In 2013 the CDC designated C. difficile as an Urgent Threat. These trends were related to the emergence of epidemic strains, in particular epidemic 027. Epidemic 027 causes about a third of CDI in the U.S. and has a tendency to cause severe disease. The firstline drug metronidazole is now more prone to fail today than 30 years ago. Our study suggests that metronidazole resistance is one hitherto overlooked factor that is driving treatment failures. This proposal seeks to understand the impact of resistance on treatment responses to metronidazole and the genetic basis for metronidazole resistance (MTZ-R) in C. difficile. We discovered that a subset of epidemic 027 strains display decreased susceptibility to metronidazole, when tested in fresh heme. Using fresh heme, we identified other metronidazole-resistant epidemic strains from different lineages. Heme induces the expression of metronidazole resistance that is otherwise not detected. We demonstrate that resistance occurs during therapy in animals and it could be selected in lab- media. This work has significant implications for public health care, because the impact of metronidazole resistance is not well characterized. Our study will provide insights to how resistance affects treatment responses to metronidazole and will unveil how it evolved in epidemic 027 and other lineages. Aim 1. To characterize the clinical impact of MTZ-R. This uses a biobank of patient stools to assess colonization with resistant strains, the on-therapy rise of resistance and if it hinders responses to MTZ. Further validations are done in a clinically reflective in vitro and animal models of CDI. Aim 2. To test if the low colonic levels of MTZ facilitates on-therapy development of MTZ-R and if it is ineffective in CDI with MTZ-R strains. MTZ will be compared to a non-absorbed MTZ analog to quantify the emergence of MTZ-R in low and high drug levels in CDI animals. The non-absorbed MTZ analog will also test the importance of high drug levels in the colon for resolving CDI due to resistant strains. Aim 3. To elucidate the evolution of MTZ-R from laboratory and patient isolates. This aim moves the C. difficile field forward to link phenotypes to their resistance genotypes and elucidates the evolutionary basis of metronidazole resistance in three settings: lab-media, animal models and clinical isolates from patients. It then applies computational genomics and molecular experimentation to identify and validate convergent or divergent paths to resistance. Public health. The