Normal flora refers to the microorganisms that normally inhabit various areas of the human body. There are two types of normal flora: resident flora that are always present, and transient flora that are temporary. Normal flora can have mutualistic or commensal relationships with the human body. Common sites inhabited by normal flora include the skin, conjunctiva, nasopharynx, oral cavity, gastrointestinal tract, and urogenital tract. The types of microbes found in these areas include various bacteria such as staphylococci and streptococci. Normal flora provides advantages to the human body by preventing pathogen growth and producing vitamins.
2. NORMAL FLORA
Normal flora is the mixture of micro-organisms (bacteria
and fungi) that are regularly found at any anatomical site
of human body is known as microbiota or normal flora.
3.
4. Resident flora:
Microbes that are always present on or within body.
Transient flora: Microbes that live in or on the body for a
period of time (hours, days, weeks, months) then move on
or die off.
5. SYMBIOTIC RELATIONSHIP
1. Mutualistic
- Both organisms benefit - “mutually beneficial”.
2. Commensalistic
- One organism benefits, the other is neither helped nor
harmed.
6. 3. Opportunistic
- Under normal conditions, microbe does not cause
disease, but if conditions become conducive, it can cause
disease.
7. The common sites of finding normal bacterial flora
are:
- Skin.
- Conjunctiva.
- Nasopharynx.
- Oral cavity.
- Gastrointestinal tract and rectum.
- Urogenital tract.
8. NORMAL FLORA OF THE SKIN
1. Skin is constantly exposed to and is in contact with the
environment, the skin is particularly apt to contain
transient micro-organisms.
2. The predominant resident micro-organisms of the skin
are aerobic and anaerobic diphtheroid bacilli (e.g.,
Corynebacterium, Propionibacterium).
9. 3. Non-hemolytic aerobic and anaerobic staphylococci
(Staphylococcus epidermidis, occasionally S.aureus and
Peptostreptococcus species); Gram-positive, aerobic,
spore-forming bacilli that are present everywhere in air,
water, and soil; 𝛼 −
ℎ𝑒𝑚𝑜𝑙𝑦𝑡𝑖𝑐 𝑠𝑡𝑟𝑒𝑝𝑡𝑜𝑐𝑜𝑐𝑐𝑖 (𝑣𝑖𝑟𝑖𝑑𝑎𝑛𝑠 𝑠𝑡𝑟𝑒𝑝𝑡𝑜𝑐𝑜𝑐𝑐𝑖) 𝑎𝑛𝑑
enterococci (enterococcus species); 𝑎𝑛𝑑 𝐺𝑟𝑎𝑚 −
𝑛𝑒𝑔𝑎𝑡𝑖𝑣𝑒 𝑐𝑜𝑙𝑖𝑓𝑜𝑟𝑚 𝑏𝑎𝑐𝑖𝑙𝑙𝑖 𝑎𝑛𝑑 𝐴𝑐𝑖𝑛𝑒𝑡𝑜𝑏𝑎𝑐𝑡𝑒𝑟.
10. NORMAL FLORA OF CONJUNCTIVA
The conjunctiva is relatively free from bacteria due to the
presence of lysozyme in the tears, which flushes the
bacteria. Predominant organisms of the eyes are:
Moraxella, diphtheroids, Staphylococcus epidermidis and
non-hemolytic streptococci.
11. NORMAL FLORA OF NASOPHARYNX
The nasopharynx is a natural habitat of the common
pathogenic bacteria causing infection of the nose, throat,
bronchi and lungs. The flora of nose harbors:
Diphtheroids, Staphylococcus, Streptococcus,
Haemophilus, and Moraxella lacunata.
12. NORMAL FLORA OF THE MOUTH
The mouth contains micrococci, Gram-positive aerobic
spore bearing bacilli, coliforms, Proteus and lactobacilli.
The gums, pockets between the teeth and crypts of the
tonsils have a wide spectrum of anaerobic flora like
fusiform bacilli, treponemes, lactobacilli, etc. Candida is
also found.
13. NORMAL FLORA OF GASTROINTESTINAL
TRACT
1. The gastrointestinal tract of the fetus in utero is sterile.
2. It becomes contaminated with organisms shortly after
birth.
3. In breast fed infants, the intestine contains lactobacilli,
enterococci, colon bacilli and staphylococci.
14. 4. Lactobacilli and enterococci predominate in the
duodenum and proximal ileum.
5. The bacterial flora is similar in lower ileum, caecum
and rectum.
6. The anaerobic condition of colon is maintained by
aerobic bacteria, which utilizes the free oxygen.
15. NORMAL FLORA OF THE GENITOURINARY
TRACT
1. Mycobacterium smegmatis, a harmless commensal is
found in the secretions (smegma) of both males and
females genitalia.
2. Strains of Mycoplasma and Ureaplasma are frequently
present as part of normal flora.
16. 3. Gardnerella vaginalis, bacteroides and alpha
streptococci have been found in penile urethra.
4. Female urethra is either sterile or contains
Staphylococcus epidermidis.
5. Doderlien bacilli remain in the vagina till menopause.
17. ADVANTAGES OF NORMAL FLORA
1. They prevent or suppress the entry of the pathogens.
2. These synthesize the vitamins especially vitamin K and
several B group viatmins.
3. The normal flora evokes the antibodies production.
18. 4. Colonies produced by some organisms of normal flora
have a harmful effect on the pathogens.
5. Endotoxins liberated by normal flora may help the
defense mechanism of the body.
