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

项目摘要 艰难梭菌感染（CDI）是世界范围内腹泻相关性腹泻和死亡的主要原因。作为 因此，美国疾病控制和预防中心将C.艰难梭菌（CD）是一个紧迫的公共卫生威胁。最近的指导方针， 美国传染病学会和美国卫生保健流行病学学会推荐口服 万古霉素或非达霉素用于非重度和重度CDI病例。由于非达霉素的高成本， 万古霉素现在是首选药物，使其成为治疗CDI的最重要抗生素。 这项工作的基础是基于我们最近在得克萨斯州的患者中发现的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 来自德克萨斯州的438名患者和来自肯尼亚的98名患者的粪便中存在甲硝唑和万古霉素， 易感CD分离株。在来自休斯顿的粪便中，114/438（26%）培养出对大肠杆菌不敏感的CD分离株。 甲硝唑组128/438例（29%），甲硝唑和万古霉素联合组97/438例（22%）。之间 在肯尼亚患者中，66/98（67%）对万古霉素不敏感，83/98（85%）对甲硝唑不敏感，57/98（85%）对甲硝唑不敏感。 (58%）。令人担忧的是，来自这两个地点的许多分离株显示出对 这些抗生素远远超过了它们已知的MIC。全基因组测序显示， vanA和vanB基因簇的同源物，是许多人中高水平万古霉素耐药的共同介质， 医院相关病原体。到目前为止，这种高水平的万古霉素不敏感性尚未报告， CD菌株。对万古霉素耐药的CD菌株的传播，万古霉素是治疗这种危及生命的疾病的一线抗生素。 病原体，将有严重的临床和公共卫生的影响。这突出表明迫切需要 全面分析循环菌株、耐药机制及其如何影响临床结果 帮助临床决策。我们的初步证据强烈支持万古霉素的假设 非敏感CD菌株可能广泛存在于CDI患者人群中， 非洲大陆可能与北美流行的菌株在遗传上不同。探讨 根据这一假设，我们将（i）评估来自德克萨斯州和肯尼亚的CDI患者感染万古霉素的比例 非敏感菌株，并比较感染菌株;（ii）表征与 万古霉素不敏感;和（iii）前瞻性随访感染万古霉素不敏感的CDI患者 菌株，以评估疾病严重程度、临床结果和治疗后感染的复发率。 由于目前万古霉素在CDI治疗中的重要性，拟议的研究将具有重大意义。 影响临床决策。重要的是，导致高水平万古霉素非- CD菌株的易感性以及它如何影响疾病的严重程度、临床结果和治疗， 确立了习这将提供对抵抗程度的深入了解，并为长期 预防和干预策略，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.