Streptococcus canis is a common colonizing bacterium of the urogenital tract of cats and dogs that can also cause invasive disease in these animal populations and in humans. Although the virulence mechanisms of S. canis are not well-characterized, an M-like protein, SCM, has recently identified been as a potential virulence factor. SCM is a surface-associated protein that binds to host plasminogen and IgGs suggesting its possible importance in host-pathogen interactions. In this study, we developed in vitro and ex vivo blood component models and murine models of S. canis vaginal colonization, systemic infection, and dermal infection to compare the virulence potential of the zoonotic S. canis vaginal isolate G361 and its isogenic SCM-deficient mutant (G361∆scm). We found that while S. canis establishes vaginal colonization and causes invasive disease in vivo, the contribution of the SCM protein to virulence phenotypes in these models is modest. We conclude that SCM is dispensable for invasive disease in murine models and for resistance to human blood components ex vivo, but may contribute to mucosal persistence, highlighting a potential contribution to the recently appreciated genetic diversity of SCM across strains and hosts.

中文翻译：

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犬链球菌定殖和疾病的新型模型揭示了M-like（SCM）蛋白的适度贡献

犬链球菌是猫和狗泌尿生殖道的常见定殖细菌，也可在这些动物种群和人类中引起侵袭性疾病。尽管犬链球菌的毒力机制尚未很好地表征，但最近已将M样蛋白SCM鉴定为潜在的毒力因子。SCM是与宿主纤溶酶原和IgG结合的表面相关蛋白，表明其在宿主与病原体相互作用中的重要性。在这项研究中，我们开发了犬链球菌阴道定植，全身感染和皮肤感染的体外和离体血液成分模型和鼠模型，以比较人畜共患犬链球菌的毒力潜力。阴道分离物G361及其同基因SCM缺陷型突变体（G361∆ scm）。我们发现，尽管犬链球菌建立了阴道定植并在体内引起侵袭性疾病，但在这些模型中，SCM蛋白对毒力表型的贡献是适度的。我们得出的结论是，SCM对于鼠类模型中的侵袭性疾病和离体对人体血液成分的抗性都是必不可少的，但可能会导致粘膜持久性，从而突出说明了最近对菌株和宿主之间SCM遗传多样性的潜在贡献。