Role of commensal species
One of the next challenges will be to understand more precisely the role of commensal species composing the skin microbiota. Multiple researches have shown that Propionibacterium acnes, newly called Cutibacterium acnes, comprised different phylotypes, some of them linked to acne pathogenicity. Recently, Nakatsuji et al. (2017) reports evidence that the community of bacteria residing on normal human skin provides protection against S. aureus. Subsequently, isolated S. hominis A9 strain from normal skin was used to produce a Sh-lantibiotics with selective and efficient activity against S. aureus .
Diversity and balance matter
The diversity of skin microbiota is associated to healthy skin when its value is high. In the case of psoriasis, a high-resolution shotgun metagenomics method was used to characterise the microbiome of psoriatic patients. Results showed decrease diversity and increase in Staphylococcus with potential strain-level variations as key determinants of the psoriatic microbiome . An interesting comparative study between the microbiota of Yanomami indians and US citizens led to the conclusion that the Yanomami indians exhibited highest bacterial diversity and westernisation severely seems to affect human skin micro biome diversity .
The advanced research on skin microbiota exposed new challenges. The determination at the strain level of commensal species (Staphylococcus epidermis, C. acnes) could help to find new specific targets and solutions to restore the balance between microorganisms. If the balance of the skin microbiota and the diversity are complex to define, the lost of equilibrium must be prevent to keep microbial homeostasis. New active ingredients, taking into account the skin microbiota, can create or help to restore an environment for its protection and the protection of the skin.