Cutaneous

Cutaneous microbiota is extremely diverse. Its composition varies according to the cutaneous zone and between individuals, and its imbalance is associated with skin diseases.

Cutaneous microbiota is particularly complex, with extremely significant inter- and intra-individual variations.1 It is composed of a set of microorganisms, bacteria, yeasts, viruses, and parasites. At least 19 major families of bacteria have been identified: the primary ones are Actinobacteria (Corynebacterium, etc.), Firmicutes (Staphylococcus, Streptococcus, etc.) and Proteobacteria (Acinetobacter, etc.).1,2 Among the bacterial strains present on healthy skin, the primary ones found are Corynebacterium jeikeium, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis.3 Microbiota composition varies based on the location, ranging from 100 microorganisms per cm2 on the back or the tips of the fingers to 106 on the forehead or in the armpits.2

This microbiota develops from birth, as a result of the contact with the vaginal flora after a vaginal birth or with the stomach flora in the case of a caesarean section. It then changes with age.5 It also varies according to gender4 and is influenced by an individual’s health status and lifestyle: immune status, hygiene, use of antibiotics, cosmetics, type of clothing, occupation, climate, geographic location, or exposure to UV.1,2,6

In adults, the surface of the skin represents between 1.5 and 2 square meters, so the cutaneous microbiota plays a fundamental defensive role against surrounding infectious agents. S. epidermidis, for example, produces antimicrobial peptides and Propionibacterium acnes contributes to the skin’s acidity.2 These two strains are also involved in topical immunity.7 Beyond that, this microbiota may modulate the systemic immune system, in the same way as the intestinal microbiota.8,9

Interactions between these microorganisms are innumerable and disruptions in this equilibrium are associated with skin problems like acne, diseases such as psoriasis or atopic dermatitis, or even abnormal wound healing.2

Sources
1- Catherine Dunyach-Remy et al. Le microbiote cutané: étude de la diversité microbienne et de son role dans la pathogénicité. Revue Francophone des Laboratoires, Février 2015 – N°469 : 51-58. http://linkinghub.elsevier.com/retrieve/pii/S1773035X15728212?via=sd
2- A. Schwiertz (Ed.) Microbiota of the Human Body. Advances in Experimental Medicine and Biology 902: 61-81. http://link.springer.com/book/10.1007%2F978-3-319-31248-4
3- Chiller K et al. Skin microflora and bacterial infections of the skin. J Investing Dermatol Symp Proc 2001; 6: 170-4. https://www.ncbi.nlm.nih.gov/pubmed/11924823
4- Fierer N. et al. The influence of sex, handedness and washing on te diversity of hand surface bacteria. Proc Natl Acad Sci USA 2008; 105:17994-9. http://www.pnas.org/content/105/46/17994.abstract
5- Somerville DA. The normal flora of the skin in different age groups. Br J Dermatol 1969;81:248-58. https://www.ncbi.nlm.nih.gov/pubmed/5778713
6- McBride ME et al. The environment and the microbial ecology of human skin. Appl Environ Microbiol 1977; 33:603-8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC170732/
7- Christensen GJM et al. Bacterial skin commensals and their role as host guardians. Benefic microbes 2014 ; 5 : 201-215. https://www.ncbi.nlm.nih.gov/pubmed/24322878
8- Belkaid Y et al. Dialogue between skin microbiota and immunity. Science 2014 ; 346 :954-959. https://www.ncbi.nlm.nih.gov/pubmed/25414304
9- Nakamizo S et al. Commensal bacteria and cutanueous immunity. Semin Immunopathol 2015 ; 37 ;73-80. https://www.ncbi.nlm.nih.gov/pubmed/25326105

Pathologies

Dysbiosis can cause multiple pathologies with repercussions on different organs.

Affecting the microbiota

There is 1 way to affect the equilibrium of microbiota.

  • Probiotics

    The WHO defines probiotics as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host”.
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The various microbiota

Intestinal

The intestinal microbiota is an organ in its own right.
Better characterized thanks to metagenomics, it is gradually giving up its secrets. Highly diversified, it lives in close relationship with its host. Formed from birth, it is specific to each individual and fulfills different functions within the body: barrier effect, trophic, metabolic and immune functions, etc., as well as others that remain to be elucidated.

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Vaginal

The vaginal microbiota is an ecosystem constituted of microorganisms, where the genus Lactobacillus predominates. Its equilibrium is fragile and changes in its composition cause infections.

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ENT

The ENT microbiota is an extremely diverse microbiota which is assumed to include at least 700 different species.

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Cutaneous

Cutaneous microbiota is extremely diverse. Its composition varies according to the cutaneous zone and between individuals, and its imbalance is associated with skin diseases.

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Pulmonary

The pulmonary microbiota was unknown for a long time, since it was commonly accepted that healthy lungs are sterile. This paradigm was cast into doubt with the discovery of the various human microbiota.

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Urinary

The urinary microbiota was discovered very recently and has only begun to be described. Imbalances in this flora may be associated with problems in the urinary tract.

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