- The skin has a normal flora of resident and transient microorganisms that protect against pathogens. Common resident bacteria include Staphylococcus epidermis and S. aureus. Fungal colonies such as Trichosporon cutaneum and Microsporum gypseum are also present.
- The skin flora provides protection from external invaders through competing for resources and producing antimicrobial substances. Some flora, like P. acnes, can stimulate immunity but also potentially cause infections under certain conditions.
- Factors like dryness, low pH from organic acids, and inhibitory substances in sweat and sebum help discourage colonization by pathogenic microorganisms on the skin.
3. Skin
Human adult has two square meters of skin
• Skin is the organ of the human body that protects
from the pathogens from the environment and
retards the loss of excessive water.
• Its other functions are insulation,
temperature regulation, sensation and synthesis
of vitamin D.
• The skin is composed of the epidermis , dermis and fat
cells.
4. Epidermis
• This layer consist of dead cells( without nucleus) and
constantly in contact with microorganism from the
environment.
• Impermeable to microorganism; however cuts,
abrasion and wounds can allow the organisms to
penetrate.
5. Dermis
• Consist of connective tissues and cushions the body
from heat and strain.
• Has sebaceous gland, sweat gland, hair follicles and
nerve endings.
Hypodermis
• It attaches the dermis layer to the underlying bones
and provides with blood.
• It functions as padding and insulation.
7. WHAT IS NORMAL FLORA ?
mixture of microorganisms regularly found at on
/ within the body of a healthy person.
Some of these microorganisms are found in
association with humans / animals only.
Definition
Normal flora is the mixture of microorganisms
(bacteria and fungi) that are regularly found at
any anatomical site of human body.
8. Normal Skin Flora
The skin is hostile to the survival and growth of
microorganisms.
Skin flora can be commensalistic, mutalistic or
pathogenic.
The flora depends on the area, the clothing,
occupation and environment.
e.g. Pathogen Streptococcus pyogenes does not survive
for more than a few hours when applied to the skin
whereas it may survive in room air for weeks.
9. Microorganisims that normally live on or in
any part of the body with out causing disease
Two basic types of Normal Flora:
Resident Normal Flora – normally GROW on/in
indicated body site,presence fixed in body.
Transient Normal Flora – only TEMPORARILY
PRESENT on/in indicated body site, usually don’t
become firmly attached but simply die within hours.
Transient microbes: in contact with environment
10. Resident microbes
Areas of high moisture content
(Axilla, groin, toe webs, perineum, scalp)
Neither profuse sweating nor washing
significantly modifies normal skin flora
Soap or disinfectant diminish microbial population
Soap: physically removes organisms
11. disinfectant. : an agent that frees from infection;
especially : a chemical that destroys vegetative forms
of harmful microorganisms (as bacteria and fungi)
especially on inanimate objects but that may be less
effective in destroying spores.
But Normal Flora rapidly replenished(restore to a
former level or condition) from sebaceous and sweat
glands
12. ROLE OF NORMAL FLORA
Immunostimulation
a) They produce antibodies which may
contribute to host defenses.
b) Some of these antibodies may
cross react with normal tissue
components.
May be source of opportunistic infections
e.g. : In Patients with impaired defence Mechanisms
13. •Protection from External Invaders
a) Because of the normal flora occupy body's
epithelial surfaces, they are able to prevent other
bacteria by blocking receptors
b) competing for essential nutrients
c) producing anti-bacteria substances
e.g. : Fatty acids, peroxides , Bacteriocins.
Nutrition
Some of the normal intestinal flora
e.g. E. coli & Bacteroids produce Vitamin K in the gut
which is available for use by host.
14. Some of the common flora on skin are:
Bacteria:
Staphylococcus aureus – folliculitis, boils, etc.
Staphylococcus epidermis - Impetigo, Abscess
Pseudomonas aeroginosa - Folliculitis
15. Folliculitis & Impetigo
Folliculitis is a common skin condition in which hair
follicles become inflamed. It's usually caused by a bacterial
or fungal infection. At first it may look like small red
bumps or white-headed pimples around hair follicles —
the tiny pockets from which each hair grows.
Impetigo is a bacterial skin infection. It causes red sores
that can break open, ooze fluid, and develop a yellow-
brown crust. These sores can occur anywhere on the
body. Impetigo is one of the most common skin infections
in children. It can occur in adults but is seen far more often
in children.
21. White Piedra & Dermatophytosis
White Piedra is an unusual asymptomatic superficial
fungal infection of the hair, characterized by the
presence of numerous, discrete, soft, asymptomatic
nodules loosely attached to the infected hair shafts. It
may occur on the scalp, eyebrows, eyelashes, beard,
axilla or in the groin.
Dermatophytosis, also known as ringworm, is
a fungal infection of the skin. Typically it results in a
red, itchy, scaly, circular rash. Hair loss may occur in
the area affected.
22. There are some microbes present on skin which
actually increase the immunity to fight pathogenic
organisms
e.g. P. Acnes inhibits the growth of many pathogenic
microorganisms but under some conditions the
organism can even cause infection( i.e. acne vulgaris)
23. FACTORS RESPONSIBLE FOR
DISCOURAGING
MICROBIAL COLONIZATION ON SKIN
1. DRYNESS:
Dry surface is inhibitory to microbial growth.
Some regions of the skin are moist than others, e.g.
The axillary region, toe webs and the perineum( skin
at the lower end of the trunk between the thighs.)
These regions has higher number of normal flora
organisms than the drier area of skin.
24. 2. Low Ph:
Skin has a normal pH between 3 and 5 and it is higher
in moist regions.
This low pH is due to the lactic acid or other organic
acids produced by normal skin microorganisms such
as staphylococci. This factor discourages the growth of
other organisms.
3. Inhibitory Substances:
Sweat glands – secrete lyzozyme that destroys bacterial
cell walls.
25. Sebaceous glands – secrete complex lipids which
may be partially degraded by Propionibacterium
acnes, that results in long chained unsaturated fatty
acids e.g. Oleic acid. This fatty acids are highly toxic
to other bacteria.
BENEFIT OF SKIN FLORA
The benefits bacteria can offer include preventing
transient pathogenic organisms from colonizing the
skin surface, either by competing for nutrients,
secreting chemicals against them, or stimulating the
skin's immune system.
26. DISADVANTAGE OF SKIN FLORA
Even resident microbes can cause skin diseases and
enter the blood system creating life-threatening
diseases particularly in immuno suppressed people.
27. WHY ARE ARMPITS
SMELLY?
1. Anaerobic bacteria in the pit use sebum
from sweat glands to produce short
chain fatty acids
2. The sweat and sebum produced by the
pit is naturally aromatic
3. Use of deodorants with antibacterial
substances, inhibit growth of G(+), may
lead to growth of G(-) MOs and infection
