Rickettsial Zoonoses Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Rickettsial Zoonoses Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Infect Immun. 2021 Mar 17;89(4). doi: 10.1128/IAI.00626-20.
, the etiological agent of Rocky Mountain spotted fever (RMSF), a life-threatening tick-borne disease that affects humans and various animal species, has been recognized in medicine and science for more than 100 years. Isolate-dependent differences in virulence of have been documented for many decades; nonetheless, the specific genetic and phenotypic factors responsible for these differences have not been characterized. Using and methods, we identified multiple phenotypic differences among six geographically distinct isolates of , representing isolates from the United States, Costa Rica, and Brazil. Aggregate phenotypic data, derived from growth in Vero E6 cells and from clinical and pathological characteristics following infection of male guinea pigs (), allowed separation of these isolates into three categories: nonvirulent (Iowa), mildly virulent (Sawtooth and Gila), and highly virulent (Sheila Smith, Costa Rica, and Taiaçu). Transcriptional profiles of 11 recognized or putative virulence factors confirmed the isolate-dependent differences between mildly and highly virulent isolates. These data corroborate previous qualitative assessments of strain virulence and suggest further that a critical and previously underappreciated balance between bacterial growth and host immune response could leverage strain pathogenicity. Also, this work provides insight into isolate-specific microbiological factors that contribute to the outcome of RMSF and confirms the hypothesis that distinct rickettsial isolates also differ phenotypically, which could influence the severity of disease in vertebrate hosts.
落矶山斑点热（RMSF）是一种危及生命的蜱传疾病，其病原体是斑疹热立克次体，它已经在医学和科学领域被认识了 100 多年。几十年来，人们已经记录了多种依赖于分离株的斑疹热立克次体毒力差异；然而，导致这些差异的特定遗传和表型因素尚未得到明确。通过使用定量和定性方法，我们鉴定了来自美国、哥斯达黎加和巴西的六个地理上不同的斑疹热立克次体分离株之间的多种表型差异。来自 Vero E6 细胞生长和感染雄性豚鼠（）后的临床和病理特征的综合表型数据，将这些分离株分为三类：非毒力（爱荷华州）、轻度毒力（锯齿和吉拉）和高毒力（希拉·史密斯、哥斯达黎加和泰亚苏）。11 种公认或假定的毒力因子的转录谱证实了轻度和高度毒力分离株之间的分离株依赖性差异。这些数据证实了以前对菌株毒力的定性评估，并进一步表明，细菌生长和宿主免疫反应之间的关键且以前未被充分认识的平衡可能会利用菌株的致病性。此外，这项工作深入了解了导致 RMSF 结局的分离株特异性微生物因素，并证实了这样一种假设，即不同的立克次体分离株在表型上也存在差异，这可能影响脊椎动物宿主疾病的严重程度。
