Servicio de Microbiología, Hospital Universitario Ramón y Cajal and Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain.
Network Center for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Front Immunol. 2021 Dec 1;12:774018. doi: 10.3389/fimmu.2021.774018. eCollection 2021.
The epidermis constitutes a continuous external layer covering the body, offering protection against bacteria, the most abundant living organisms that come into contact with this barrier. The epidermis is heavily colonized by commensal bacterial organisms that help protect against pathogenic bacteria. The highly regulated and dynamic interaction between the epidermis and commensals involves the host's production of nutritional factors promoting bacterial growth together to chemical and immunological bacterial inhibitors. Signal trafficking ensures the system's homeostasis; conditions that favor colonization by pathogens frequently foster commensal growth, thereby increasing the bacterial population size and inducing the skin's antibacterial response, eliminating the pathogens and re-establishing the normal density of commensals. The microecological conditions of the epidermis favors Gram-positive organisms and are unsuitable for long-term Gram-negative colonization. However, the epidermis acts as the most important host-to-host transmission platform for bacteria, including those that colonize human mucous membranes. Bacteria are frequently shared by relatives, partners, and coworkers. The epidermal bacterial transmission platform of healthcare workers and visitors can contaminate hospitalized patients, eventually contributing to cross-infections. Epidermal transmission occurs mostly the hands and particularly through fingers. The three-dimensional physical structure of the epidermis, particularly the fingertips, which have frictional ridges, multiplies the possibilities for bacterial adhesion and release. Research into the biology of bacterial transmission the hands is still in its infancy; however, tribology, the science of interacting surfaces in relative motion, including friction, wear and lubrication, will certainly be an important part of it. Experiments on finger-to-finger transmission of microorganisms have shown significant interindividual differences in the ability to transmit microorganisms, presumably due to genetics, age, sex, and the gland density, which determines the physical, chemical, adhesive, nutritional, and immunological status of the epidermal surface. These studies are needed to optimize interventions and strategies for preventing the hand transmission of microorganisms.
表皮构成了覆盖身体的连续外部层，提供了抵御细菌的保护，细菌是与这道屏障接触最多的生物体。表皮被大量共生细菌定植，这些细菌有助于抵御病原菌。表皮与共生菌之间高度调节和动态的相互作用涉及宿主产生促进细菌生长的营养因子，同时产生化学和免疫细菌抑制剂。信号转导确保了系统的内稳态；有利于病原体定植的条件通常促进共生菌的生长，从而增加细菌种群规模，并诱导皮肤的抗菌反应，消除病原体并重新建立正常的共生密度。表皮的微生态条件有利于革兰氏阳性菌，不适合革兰氏阴性菌的长期定植。然而，表皮是细菌最重要的宿主间传播平台，包括定植于人体黏膜的细菌。细菌经常在亲属、伴侣和同事之间共享。医护人员和访客的表皮细菌传播平台会污染住院患者，最终导致交叉感染。表皮传播主要发生在手部，特别是通过手指。表皮的三维物理结构，特别是具有摩擦脊的指尖，增加了细菌黏附和释放的可能性。手部细菌传播生物学的研究仍处于起步阶段；然而，摩擦学，即相对运动中相互作用表面的科学，包括摩擦、磨损和润滑，肯定是其中的重要组成部分。手指到手指之间微生物传播的实验表明，个体之间在传播微生物的能力上存在显著差异，这可能归因于遗传、年龄、性别以及决定表皮表面物理、化学、黏附、营养和免疫状态的腺体密度。这些研究对于优化干预措施和预防微生物通过手部传播的策略是必要的。
