stratum corneum, lysozyme, pH 5. The fact that the normal pH of the skin surface plays
a significant role in local immunity is now considered indisputable [7, 10].
A common theory is that skin acidity (pH) plays an important role in its
antimicrobial protection. The normal condition of the skin is sour, it is supported by
the secretion of sweat glands, sebum, and the secretion of fatty acids by epidermal
staphylococci. Therefore, it is believed that the resident microflora of the skin (that is,
normoflora) also partly supports the acidic pH of the skin.
Normal (resident) flora grows better at acidic pH, while pathogenic bacteria, for
example, golden staphylococci, prefer a neutral pH. Thus, more acidic pH protects the
skin from colonization by non-resident and pathogenic bacteria [8].
Acids produced by the resident microflora (normophyllores) are also part of the
local mechanisms of protection and are dependent on the normal microflora. For
example, Staphylococcus epidermidis, Propionibacterium acnes, Pityrosporum ovale,
Corynebacteria produce specific enzymes of lipase and esterase, break down
triglycerides into free fatty acids, which results in a decrease in the pH of the skin
surface and thus forms adverse conditions for pathogenic microorganisms that a person
comes in contact with on a daily basis.
Normal flora also acts as a barrier and serves to prevent invasion and the growth
of pathogenic bacteria. Healthy growth and maintenance of a resident flora effectively
prevents colonization of the skin by transient bacteria, including Escherichia coli,
Pseudomonas, Staphylococcus aureus, Sandida albicans.
The most characteristic skin microbes are corneum bacteria, which make up 70 %
of the normal skin of the microflora (Corynebacterium bovis, C. lipophylicum,
C. minutissimus,
C.
pseudodiphtheriticum,
C.
xerosis);
Propionibacteria
(Propionibacterium
acnes,
P. avidum,
P. freudenreichii,
P. granulatum);
staphylococci (Staphylococcus epidermidis, S. saprophyticus, S. capitis, S. cohnii);
micrococci (Micrococcuskristinae, M.luteus, M.varians); Sarcini (Sarcina maxima,
S. ventriculi);
actinomycetes
(Actinomyces
bovis,
A. israelii);
mushrooms
(Pityrosporum ovale, P. orbiculare). In some individuals there are yeast molds
Candida, Staphylococcus aureus, various streptococci, anaerobic clostridia [2].
At one square inch of skin can be from 10,000 to 1 million bacterial cells. The
microflora of the skin of the face differs from the flora of hands or other parts of the
body. More microorganisms on areas of skin covered with hair. The composition of
bacterial strains on the skin varies depending on the area of the skin.
High density of bacteria is found on the skin with less acidic pH: genitalia, anus,
folds under the mammary glands, armpits. Dry and open areas of the skin have a lower
pH and a lower density of microorganisms. For example, the inner surface of the
forearm has a bacterial population (in colonies forming units) 10
2
-10
3
CFU/cm
2
-
compared with 10
5
CFU cm
2
in the axillary basins.
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