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

 描述(申请人提供)：艰难梭菌感染(CDI)目前是美国医院获得性和抗生素相关性腹泻的最常见可定义原因，估计每年的治疗总成本在10至48亿美元之间。艰难梭菌(Cd)是一种耐多药的革兰氏阳性厌氧菌，在抗生素治疗改变肠道微生物区系后，在结肠中大量繁殖。因此，抗生素治疗是CDI的主要危险因素。治疗受到致病菌株毒力增加、芽胞形成、复发和治疗中使用的抗生素的阻碍，这些抗生素扰乱了结肠微生物区系的组成和定植耐药性。因此，迫切需要非抗生素治疗来保护结肠微生物区系。这项研究将评估FDA批准的基于水杨酸盐的改变用途的药物作为CDI的新的非抗生素治疗方法，而不改变肠道微生物区系。致病CD菌株产生毒素A和B，这两种毒素直接导致疾病，因为只有产生这两种毒素之一的菌株才会引起疾病。因此，抑制毒素合成或毒素活性，直接针对结肠损伤和疾病的原因，是对抗CDI的一种有前途的方法。我们已经确定CD毒素受到Quorum信号的严格调控，并发现目前用于治疗疼痛和炎症的某些FDA批准的水杨酸盐类药物抑制了超强毒力和非超强毒力CD菌株的毒素合成。我们还发现吲哚是一种有效的镉毒素活性抑制剂。吲哚主要由肠道微生物区系产生，是色氨酸代谢的最终产物。在毒素抑制浓度下，这些化合物都不会影响Cd的生长。这是第一批CD毒素合成的抑制剂，被认为是潜在的治疗CDI的非抗生素药物。我们的中心假设是，这些抑制物阻断了毒素合成调控途径，从而阻止了毒素基因的转录。在这里，我们将(I)确定这些水杨酸酯类抑制剂的靶点和抑制机制，(Ii)评估它们的体外疗效 抗临床CD分离株，以及(Iii)检查这些毒素合成的鸡尾酒的效果 和毒素活性抑制剂作为预防CDI诱导的炎症、结肠病理和CDI模型复发的联合治疗。在该项目的结束时，将建立关于镉毒素调节和发病机制的新知识，并确定新的治疗方法。具体地说，我们将对这些cd毒素抑制剂的靶点和抑制机制有一个新的理解，最重要的是，一个新的创新的治疗策略，使用非抗生素毒素合成和毒素活性抑制剂的鸡尾酒作为一种 联合疗法来对抗这一重大的公共卫生问题。这些临床前研究将为未来的临床试验奠定基础，以评估这些有效的毒素抑制剂在CDI治疗中的使用。我们的系，德克萨斯大学公共卫生学院传染病中心正在进行多学科研究，正在进行CD治疗和预防的临床试验。因此，我们处于战略地位，可以接触到CDI患者群体来评估这些抑制剂，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有效性。

 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.