Targeting the Toxins: A Novel Non-Antimicrobial Approach to Combat Clostridium difficile infections

 描述（由申请人提供）：艰难梭菌感染（CDI）现在是美国医院获得性和腹泻相关性腹泻的最常见可确定原因，估计每年的治疗总费用在1至48亿美元之间。C.艰难梭菌（CD）是一种多重耐药的革兰氏阳性厌氧病原体，在肠道微生物群被抗生素治疗改变后在结肠中传播。因此，抗生素治疗是CDI的主要风险因素。致病菌株的毒力增加、孢子形成、复发和治疗中使用的抗生素破坏了结肠微生物群的组成和定植抗性，阻碍了治疗。因此，迫切需要保护结肠微生物群的非抗生素治疗。这项研究将评估FDA批准的基于水杨酸盐的药物作为新型非抗生素治疗CDI而不改变肠道微生物群。致病性CD菌株产生毒素A和B，这是直接导致疾病的原因，因为只有产生这两种毒素的菌株才会导致疾病。因此，抑制毒素合成或毒素活性，直接靶向结肠损伤和疾病的原因，是对抗CDI的有希望的方法。我们已经确定CD毒素受到群体信号传导的严格调节，并且已经发现目前用于治疗疼痛和炎症的某些FDA批准的基于水杨酸盐的药物抑制超毒力和非超毒力CD菌株中的毒素合成。我们还确定吲哚作为CD毒素活性的有效抑制剂。吲哚主要由肠道微生物群作为色氨酸代谢的终产物产生。这些化合物在其毒素抑制浓度下均不影响CD生长。这些是第一个鉴定的CD毒素合成抑制剂，并证明其作为有前景的抗CDI非抗生素治疗剂的潜力。我们的中心假设是，这些抑制剂阻断毒素合成调节途径，从而阻止毒素基因的转录。在这里，我们将（i）确定这些水杨酸基抑制剂的靶点和抑制机制，（ii）评估它们的体外功效 针对临床CD分离株，和（iii）检查这些毒素合成的鸡尾酒的功效 和毒素活性抑制剂作为联合治疗预防CDI模型中CDI诱导的炎症、结肠病理和复发。在本项目结束时，将建立关于CD毒素调节和发病机制的新知识，并确定新的治疗方法。具体而言，我们将获得对这些CD毒素抑制剂的靶点和抑制机制的新理解，最重要的是，使用非抗生素毒素合成和毒素活性抑制剂的鸡尾酒作为治疗药物的新的和创新的治疗策略。 联合疗法来解决这一重大公共卫生问题。这些临床前研究将成为未来临床试验的基础，以评估这些强效毒素抑制剂治疗CDI的用途。我们的部门，中心传染病在得克萨斯州公共卫生学院的大学是从事多学科的研究与正在进行的临床试验的CD治疗和预防。因此，我们处于战略地位，可以接触CDI患者人群，以评估这些抑制剂，并进行I期和II期临床试验，以测试这种新型非抗生素疗法的疗效。

 DESCRIPTION (provided by applicant): Clostridium difficile infection (CDI) is now the most common definable cause of hospital-acquired and antibiotic-associated diarrhea in the United States, with the total cost of treatment estimated between 1 to 4.8 billion U.S. dollars annually. C. difficile (CD), a multidrug-resistant Gram-positive anaerobic pathogen, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. Thus, antibiotic therapy is a major risk factor for CDI. Treatment has been hampered by increased virulence of the causative strains, sporulation, recurrence, and antibiotics used in treatment that disrupt the composition and colonization resistance of the colonic microbiota. As a result, there is an urgent need for non-antibiotic treatments that preserve the colonic microbiota. This study will evaluate repurposed FDA-approved salicylate-based drugs as novel non-antibiotic treatments for CDI without altering the gut microbiota. Pathogenic CD strains produce toxins A and B, which are directly responsible for disease because only strains that produce either of these toxins cause disease. Therefore, inhibiting toxin synthesis or toxin activity, which directly targets the cause f colonic injury and illness, is a promising approach to combat CDI. We have established that the CD toxins are stringently regulated by quorum signaling and have discovered that certain FDA-approved salicylate-based drugs currently used to treat pain and inflammation inhibit toxin synthesis in both hypervirulent and non-hypervirulent CD strains. We have also identified indole as a potent inhibitor of CD toxin activity. Indole is primarily produced by the gut microbiota as a end product of tryptophan metabolism. None of these compounds affect CD growth at their toxin-inhibitory concentrations. These are the first inhibitors of CD toxin synthesis identified an demonstrate potential as promising non-antibiotic therapeutic agents against CDI. Our central hypothesis is that these inhibitors block the toxin synthesis regulatory pathway, thereby preventing the transcription of the toxin genes. Here, we will (i) identify the target and the mechanism of inhibition of these salicylate-based inhibitors, (ii) evaluate their in vitro efficacy against clinical CD isolates, and (iii) examine the efficacy of a cocktail of these toxin synthesis and toxin activity inhibitors as a combination therapy in preventing CDI-induced inflammation, colonic pathology, and recurrence in a CDI model. At the conclusion of this project, new knowledge about CD toxin regulation and pathogenesis will be established and novel treatment methods identified. Specifically, we will gain a new understanding of the target and mechanism of inhibition of these CD toxin inhibitors and most importantly, a new and innovative therapeutic strategy using a cocktail of both non-antibiotic toxin synthesis and toxin activity inhibitors as a combination therapy to combat this major public health problem. These preclinical studies will form the basis for future clinical trials to evaluate the use of these potent toxin inhibitors for he treatment of CDI. Our department, Center for Infectious Diseases at the University of Texas School of Public Health is engaged in multidisciplinary studies with on-going clinical trials of CD treatments and prevention. Thus, we are strategically situated with access to CDI patient population to evaluate these inhibitors and to conduct phases I and II clinical trials to test for he efficacy of this novel non- antibiotic therapy.