Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, 86011, USA.
Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011, USA.
Anaerobe. 2019 Aug;58:53-72. doi: 10.1016/j.anaerobe.2019.03.017. Epub 2019 Apr 1.
Clostridioides difficile infection (CDI) is an emerging public health threat and C. difficile is the most common cause of antimicrobial-associated diarrhea worldwide and the leading cause of hospital-associated infections in the US, yet the burden of community-acquired infections (CAI) is poorly understood. Characterizing C. difficile isolated from canines is important for understanding the role that canines may play in CAI. In addition, several studies have suggested that canines carry toxigenic C. difficile asymptomatically, which may imply that there are mechanisms responsible for resistance to CDI in canines that could be exploited to help combat human CDI. To assess the virulence potential of canine-derived C. difficile, we tested whether toxins TcdA and TcdB (hereafter toxins) derived from a canine isolate were capable of causing tight junction disruptions to colonic epithelial cells. Additionally, we addressed whether major differences exist between human and canine cells regarding C. difficile pathogenicity by exposing them to identical toxins. We then examined the canine gut microbiome associated with C. difficile carriage using 16S rRNA gene sequencing and searched for deviations from homeostasis as an indicator of CDI. Finally, we queried 16S rRNA gene sequences for bacterial taxa that may be associated with resistance to CDI in canines. Clostridioides difficile isolated from a canine produced toxins that reduced tight junction integrity in both human and canine cells in vitro. However, canine guts were not dysbiotic in the presence of C. difficile. These findings support asymptomatic carriage in canines and, furthermore, suggest that there are features of the gut microbiome and/or a canine-specific immune response that may protect canines against CDI. We identified two biologically relevant bacteria that may aid in CDI resistance in canines: 1) Clostridium hiranonis, which synthesizes secondary bile acids that have been shown to provide resistance to CDI in mice; and 2) Sphingobacterium faecium, which produces sphingophospholipids that may be associated with regulating homeostasis in the canine gut. Our findings suggest that canines may be cryptic reservoirs for C. difficile and, furthermore, that mechanisms of CDI resistance in the canine gut could provide insights into targeted therapeutics for human CDI.
艰难梭菌感染(CDI)是一种新出现的公共卫生威胁,艰难梭菌是全球最常见的抗微生物相关性腹泻的病因,也是美国医院相关性感染的主要病因,但社区获得性感染(CAI)的负担了解甚少。描述从犬类分离的艰难梭菌对于了解犬类在 CAI 中可能发挥的作用很重要。此外,有几项研究表明,犬类无症状携带产毒艰难梭菌,这可能意味着犬类存在对 CDI 的耐药机制,可以利用这些机制来帮助治疗人类 CDI。为了评估犬源艰难梭菌的毒力潜力,我们测试了从犬源分离株中获得的毒素 TcdA 和 TcdB(以下简称毒素)是否能够引起结肠上皮细胞的紧密连接破坏。此外,我们还研究了人类和犬类细胞在艰难梭菌致病性方面是否存在主要差异,方法是用相同的毒素暴露它们。然后,我们使用 16S rRNA 基因测序研究了与艰难梭菌携带相关的犬肠道微生物组,并寻找作为 CDI 指标的体内平衡失调。最后,我们对 16S rRNA 基因序列进行了查询,寻找可能与犬类对 CDI 耐药性相关的细菌分类群。从犬类分离的艰难梭菌产生的毒素能够降低体外人源和犬源细胞中紧密连接的完整性。然而,在艰难梭菌存在的情况下,犬类肠道并没有出现功能失调。这些发现支持犬类无症状携带,并进一步表明,肠道微生物组和/或犬类特异性免疫反应的某些特征可能保护犬类免受 CDI 的侵害。我们鉴定了两种可能有助于犬类对 CDI 耐药的具有生物学意义的细菌:1)希氏梭菌,其合成的次级胆汁酸已被证明能为小鼠提供对 CDI 的耐药性;2)粪肠球菌,其产生的神经鞘磷脂可能与调节犬类肠道的体内平衡有关。我们的研究结果表明,犬类可能是艰难梭菌的隐性储库,此外,犬类肠道中 CDI 耐药的机制可能为人类 CDI 的靶向治疗提供启示。
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