Department of Laboratory Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
Department of Microbiology and Immunology, Indiana University School of Medicine-Northwest, Gary, IN, USA.
Emerg Microbes Infect. 2022 Dec;11(1):1402-1415. doi: 10.1080/22221751.2022.2074316.
is an important human commensal bacteria colonizing the human body, especially the nasal cavity. The nasal carriage can be a source of bacteremia. However, the bacterial factors contributing to nasal colonization are not completely understood. By analysing strains from the nasal cavity of the children, young adults, and seniors, we found that the low activity of the SaeRS two-component system (TCS) is an important determinant for to colonize in seniors. The senior group isolates of showed a rather distinct sequence type composition as compared with other age group isolates. The senior group isolates showed not only a lower gene carriage of enterotoxins a, c, and q but also lower hemolytic activity against human red blood cells. Of regulators affecting hemolysin production (i.e. , , , , and ), only the SaeRS TCS showed an age-dependent decrease of activity. The decreased virulence and better colonization ability of the senior group isolates of were confirmed in the mouse model. The senior group isolates showed the lowest survival and the best adhesion and colonizing ability. Also, the senior nasal secretions supported survival better than the child and young adult nasal secretions. These results indicated that the senior nasal cavity favours colonization of with higher adhesion and lower virulence, to which the reduced SaeRS TCS activity contributes. Taken together, our results illustrate an example of bacterial adaptation to the changing host environment.
是一种重要的人体共生菌，定植于人体，尤其是鼻腔。鼻腔定植可能是菌血症的源头。然而，导致定植的细菌因素尚不完全清楚。通过分析来自儿童、青年和老年人鼻腔的菌株，我们发现 SaeRS 双组分系统（TCS）的低活性是定植于老年人的重要决定因素。与其他年龄组的分离株相比，老年人组的 分离株表现出截然不同的序列型组成。老年人组的分离株不仅携带较少的肠毒素 a、c 和 q 基因，而且对人红细胞的溶血活性也较低。在影响溶血素产生的调节剂（即， ， ， ，和 ）中，只有 SaeRS TCS 的活性表现出年龄依赖性下降。在小鼠模型中证实了老年人组 分离株的毒力降低和更好的定植能力。老年人组的分离株表现出最低的存活率和最佳的黏附及定植能力。此外，老年人的鼻腔分泌物比儿童和青年的鼻腔分泌物更能支持 的存活。这些结果表明，老年人的鼻腔更有利于具有更高黏附性和更低毒力的定植，而这归因于 SaeRS TCS 活性的降低。综上所述，我们的研究结果说明了细菌适应宿主环境变化的一个实例。
