Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_998_Библиотеки_им_академика_М_И_Перельмана

Most skin microorganisms are commensal or temporary passing members. The following four bacterial phyla are present on human skin: Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes. Staphylococcus, Propionibacterium and Corynebacterium are the dominant genera, and their inter-individual distribution is constant. Furthermore, on normal human skin viruses (human papillomavirus, human polyomavirus, circovirus and bacteriophages) and eukaryotes microbes (fungi and protists) are present [23]. Considering the community composition in dif­ferent individuals, it is possible to state that the microbiota of an individual is as unique as a n­gerprint [24, 25].

Microorganisms do not inhabit just the epi­dermis. Metagenomic techniques demonstrate bacterial DNA deep in the dermis too, although such a technology may not assess the viability of the associated microorganisms [12, 23]. Phagocytic cells might translocate the super­cial microbiota to a sub-epidermal level and epidermal physical barriers or antimicrobial peptides (AMPs) would serve as key regulators in the maintenance of dermal microbiome homeostasis [26]. The action of microorgan­isms below the basement membrane might be in correlation with the immunological proper­ties of the skin. The skin is an active immune organ where the keratinocytes can no longer be considered as the sole barrier against the exter­nal environment, but as components of a com­plex immune-regulatory network [27]. The resident skin bacteria provide the rst line of defence against potentially dangerous patho­gens, and produce small molecules that inu­ence the growth and behaviour of their microbial neighbours. The major innate mechanism of the antimicrobial defence of the skin consists of AMPs, such as defensins, cathelicidin LL-37 and dermicidin [28]. These peptides are emerg­ing as important tools in the control of skin pathogenic bacteria. It is proven that skin com­mensal bacteria have a promoting effect on T cell response, controlling nuclear factor-κB sig­nalling and the production of cytokines, such as tumour necrosis factor (TNF)-α and interleukin-1β [29, 30] although they can act both in synergy and in opposition to the immune system [31].

In recent years, researchers have developed programmes to investigate the molecular mecha­nism underlying benecial effects of spring waters. Aquaphilus dolomiae is a non-spore- forming bacterium belonging to the Neisseriaceae family, which is isolated from Avène thermal water (France), historically used in the manage­ment of chronic inammatory skin diseases. The incubation of human keratinocytes with I-modulia, a biological extract from cultures of Aquaphilus dolomiae, showed an upregulation of the innate immune response [39, 40]. Similarly, the lysate of Vitreoscilla liformis has been shown to enhance skin defence mechanisms and to decrease UV-induced sunburn cells in human

skin, possibly by the activation of cutaneous reg­ulatory T cells. Vitreoscilla liformis is a lamen- tous Gram-negative aerobic bacterium belonging to the Neisseriaceae family found in LaRoche­Posay thermal water (France), historically applied to manage chronic inammatory skin diseases [41, 42].