Characterizing Vancomycin-Resistant C. difficile Strains at Two Geographically Distinct Locations

项目总结 艰难梭状芽胞杆菌感染(CDI)是全球抗生素相关性腹泻和死亡的主要原因。AS 因此，美国疾控中心已将艰难梭菌(CD)列为紧急公共卫生威胁。最近的指导方针来自 美国传染病学会和美国保健流行病学学会推荐口服 对于非重症和重型CDI患者，万古霉素或非达克索米星均有效。由于非达克索米星的价格很高， 万古霉素现在是治疗CDI的首选药物，使其成为治疗CDI最重要的抗生素。 这项工作的基础是我们最近在德克萨斯州和澳大利亚的患者中发现的CD菌株 肯尼亚对甲硝唑和万古霉素的敏感性降低。我们检查了腹泻CDI 从德克萨斯州的438名患者和肯尼亚的98名患者的粪便中检测甲硝唑-和万古霉素-非... 敏感的CD分离株。在来自休斯顿的粪便中，114/438(26%)的人培养出不容易感染的CD分离株 甲硝唑耐药率为29%(128/438)，甲硝唑与万古霉素同时耐药率为22%(97/438)。其中 肯尼亚患者中，66/98(67%)对万古霉素不敏感，83/98(85%)对甲硝唑不敏感，57/98 对两种抗生素的耐药率均为58%。令人担忧的是，来自这两个地点的许多分离株都显示出对 这些抗生素远远超过了它们已知的最低抑菌浓度。全基因组测序显示 Vana和vanB基因簇的同源物，许多万古霉素高水平耐药性的常见介体 与医院有关的病原体。到目前为止，还没有报道过如此高水平的万古霉素不敏感 CD菌株。对万古霉素耐药的CD菌株的传播，万古霉素是这种危及生命的一线抗生素 病原体，将有严重的临床和公共卫生影响。这突显出迫切需要一种 综合分析循环菌株、耐药机制及其对临床结局的影响 帮助为临床决策提供信息。我们的初步证据有力地支持了万古霉素 不敏感的CD毒株可能在CDI患者人群中广泛传播，而且这种毒株在 非洲大陆可能与北美流行的病毒株在基因上不同。去调查 在这一假设下，我们将(I)评估德克萨斯州和肯尼亚的CDI患者感染万古霉素的比例 不敏感的菌株并比较感染菌株；(Ii)鉴定与 万古霉素不敏感；以及(Iii)前瞻性跟踪感染万古霉素不敏感的CDI患者 评估疾病严重程度、临床结果和治疗后感染复发率的菌株。 由于目前万古霉素在CDI治疗中的重要性，拟议的研究将有一个主要的 对临床决策的影响。重要的是，负责高水平万古霉素的遗传因素非 CD菌株的敏感性及其对疾病严重性、临床结果和治疗的影响将是 已经成立了。这将提供对阻力程度的洞察，并开辟长期的新途径 预防和干预战略，以减少与这种威胁生命的病原体相关的死亡。

PROJECT SUMMARY Clostridioides difficile infection (CDI) is the leading cause of antibiotic-associated diarrhea and death worldwide. As a result, the U.S. CDC has classified C. difficile (CD) as an urgent public health threat. Recent guidelines from Infectious Diseases Society of America and Society for Healthcare Epidemiology of America recommended oral vancomycin or fidaxomicin for both non-severe and severe CDI cases. Because of the high cost of fidaxomicin, vancomycin is now the drug of choice, making it the most important antibiotic for the treatment of CDI. The foundation for this work is based on our recent discovery of CD strains in patients from Texas and Kenya exhibiting reduced susceptibility to both metronidazole and vancomycin. We examined diarrhea CDI stools from 438 patients from Texas and 98 from Kenya for the presence of metronidazole- and vancomycin-non- susceptible CD isolates. Of the stools from Houston, 114/438 (26%) grew CD isolates that were not susceptible to vancomycin, 128/438 (29%) to metronidazole, and 97/438 (22%) to both metronidazole and vancomycin. Among the Kenyan patients, 66/98 (67%) were not susceptible to vancomycin, 83/98 (85%) to metronidazole, and 57/98 (58%) to both antibiotics. Alarmingly, many of the isolates from both locations showed levels of non-susceptibility to these antibiotics that far exceeded their known MICs. Whole-genome sequencing showed the presence of homologs of vanA and vanB gene clusters, common mediators of high-level vancomycin resistance in many hospital-associated pathogens. Until now, such high-level vancomycin non-susceptibility has not been reported in CD strains. The spread of CD strains resistant to vancomycin, a front-line antibiotic for this life-threatening pathogen, will have serious clinical and public health implications. This underscores an urgent need for a comprehensive analysis of the circulating strains, mechanisms of resistance, and how it impacts clinical outcomes to help inform clinical decisions. Our preliminary evidence strongly supports the hypothesis that vancomycin non-susceptible CD strains may be widespread in the CDI patient population and that strains circulating on the African continent may be genetically different from strains circulating in North America. To investigate this hypothesis, we will (i) assess the proportion of CDI patients from Texas and Kenya infected with vancomycin non-susceptible strains and compare the infecting strains; (ii) characterize the genetic elements associated with vancomycin non-susceptibility; and (iii) prospectively follow CDI patients infected with vancomycin non-susceptible strains to assess disease severity, clinical outcome, and rate of recurrence of the infection following treatment. Due to the current importance of vancomycin in CDI treatment, the proposed research will have a major impact on clinical decisions. Importantly, the genetic elements responsible for high-level vancomycin non- susceptibility in CD strains and how it impacts disease severity, clinical outcome, and treatment will be established. This will provide insight into the extent of resistance and open up new avenues for long-term preventative and interventional strategies to mitigate deaths associated with this life-threatening pathogen.