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NORMAL FLORA OF HUMAN BODY
DR G LOKESHWARI CMC
21.09.2011
Normal Flora
• DefinitionNormal flora is the mixture of microorganisms (bacteria and fungi) that are regularly found at any anatomical site of human body like:
Normal Flora
• Skin• Eyes (i.e. Conjunctiva)• Nose (i.e. Respiratory tract)• Mouth (i.e. Human Oral
Cavity)• Ears• Urogenital tract• Alimentary tract
Sterile tissuesIn a healthy human, the internal tissues such as:• blood• brain• muscle• cerbrospinal fluid (csf.) are normally free of microorganisms.
Normal Flora
Normal Flora
• Resident flora – Acquired rapidly during
& after birth• Transient flora
1. They constitute a protective host defense mechanism.
Importance of The Normal Flora (Advantages)
Importance of The Normal Flora (Advantages)
2. They produce vitamin B and vitamin K in intestine.
Importance of The Normal Flora (Advantages)
3.The oral flora contribute to immunity by inducing low levels of circulating and secretory antibodies that may cross react with pathogens.
Importance of The Normal Flora (Advantages)
4.The oral bacteria flora exert microbial antagonism against nonindigenous species by production of inhibitory fatty acids, peroxides, bacteriocins, etc.
Importance of The Normal Flora (Disadvantages)
1. They can cause disease in the following:
a) When individuals become immunocompromised or debilitated.
b) When they change their usual anatomic location. Eg: E.coli in UTI
c) can cause confusion in diagnosis.
Role of antibiotics on Normal flora
Eg: Pseumembranous Enterocolitis.
Estimation of the Normal flora
It has been calculated that the normal flora human body about 1012 bacteria on the skin, 1010 in the mouth, and 1014 in the gastrointestinal tract.
Normal Flora of the Skin
• The most important sites are:1.Axilla2.Groin3.Areas between the toes
Normal Flora of the Skin
• Important bacteria:1. Staphylococcus epidermidis2. Staph aureus3. Propionibacterium acne4. Streptococci viridans & faecalis.5. Pseudomonas6. Anerobes 7. Candida 8. Pityrosporum.
Normal Flora of the Cunjunctiva
1. Staphylococcus epidermidis2. Corynebacterium sp.3. Moraxella sp.4. Non-haemolytic streptococci.
Normal Flora of the Respiratory Tract
A) The nares (nostrils)
1. Staphylococcus aureus
2. Staphylococcus
epidermidis
3. Diphtheroides
4. Haemophilus sp.
5. Streptococcus pneumoniae
Normal Flora of the Respiratory Tract
B) The upper respiratory tract (nasopharynx).
1. Streptococci viridans
2. Streptococci Pyogenes
3. Streptococcus pneumoniae
4.Branhamella catarrhalis
5. Staphylococcus epidermis
6. Haemophilus influenzae
Normal Flora of the Respiratory TractC) The lower respiratory tract
(trachea, bronchi, and pulmonary tissues):
• Usually sterile.
• Commensal – Pneumocystis jiroveci
• The individual may become
susceptible to infection by
pathogens descending from the
nasopharynx e.g.
• H. influenzae
• S. pneumoniae.
Normal Flora of the Human Oral Cavity• Oral bacteria include:1. Streptococcus mitis2. Viridans streptococci3. Lactobacilli4. Staphylococci (S. aureus and S.
epidermidis)5. Corynebacterium sp.6. Bacteroides sp., Fusiform bacilli7. Streptococcus sanguis (dental
plaque)8. Streptococcus mutans (dental
plaque) 9. Actinomyces sp.
Fungus:1. Candida
The Normal Flora of The Ears (i.e. external ear)
• The external ears contains avariety of microorganisms. These include:
1. Staphylococcus epidermidis
2. Staphylococcus aureus
3. Corynebacterium sp
Normal flora of the Urogenital Tract
a) The anterior urethra1. CONS (excluding Staph saprophyticus)2. Enterococcus faecalis3. Alpha-hemolytic streptococci. 4. Lactobacillus5. Bacteroides6. Some enteric bacteria (e.g. E. coli, Proteus sp.)7. Diphtheroides.8. Acinetobacter sp.9. Mycoplasma sp.10. Chlamydia and ureaplasma11. Candida sp.(Adults and pregnancy)12. Mycobacterium smegmatis
Normal flora of the Urogenital Tractb) The vagina 1. Corynebacterium sp.2. Staphylococci3. Streptococcus agalactiae4. Escherichia coli5. Lactobacillus acidophilus6. Flavobacterium sp.8. Viridans streptococci9. Other Enterobacteriaceae10. Anaerobic cocci & bacilli11. Listeria12. Mycoplasma13. Gardenella vaginalis14. Neisseriae 15. Spirochetes
Normal flora of vulva• Sterile –till 24 hours after birth• After 24 hours – Micrococci,
Enterococci,Diphtheroids.• In first 2-3 days – similar to adult.• After 3 days – Micrococci, alpha and non-
haemolytic Streptococci,Coliforms and Diphtheroids• At Puberty – Doderline bacilli, E.coli, Yeast. • Pregnancy – Staph epidermidis, Doderlein’s, yeast.• After menopause – similar to that of before
puberty.
Normal Flora of the Gastrointestinal Tract (GIT)
• In humans, the GIT flora are influenced by:1.Age2.Diet3.Cultural conditions4.The use of antibiotics
Normal Flora of the Gastrointestinal Tract (GIT)
• At birth • The entire intestinal tract is sterile, but
bacteria enter with the first feed. The initial colonizing bacteria vary with the food source of the infant.
Normal Flora of the Gastrointestinal Tract (GIT)
• In breast-fed
1. Bifidobacteria account for more than 90% of the total
intestinal bacteria.
2. Enterobacteriaceae
3. Enterococci
4. Bacteroides
5. Staphylococci
Normal Flora of the Gastrointestinal Tract (GIT)
• In bottle-fed infants• Bifidobacteria are not predominant. When breast-fed infants are switched
to a diet of cow's milk or solid food, bifidobacteria are progressively joined by:
1. Enterics2. Bacteroides3. Enterococci4. Lactobacilli5. Clostridia
Normal Flora of the Gastrointestinal Tract (GIT)
In the upper GIT of adult humans• mainly acid-tolerant lactobacilli e.g. Helicobacter pylori
Normal Flora of the Gastrointestinal Tract (GIT)
• The proximal small intestine1. Lactobacilli2. Enterococcus faecalis3. Coliforms4. Bacteroides
The flora of the large intestine (colon)
1. Bacteroides 2. Bifidobacterium3. (Bifidobacterium bifidum) 96 to 4. Clostridia 99%4. lactobacilli 5. Anaerobic Streptococci6. Escherichia coli 8. Streptococci faecalis9. Kebsiella sp. 1 to 10. Proteus sp. 4%11. Enterobacter sp. 12. Pseudomonas aeroginosa11.Candida albicans (Yeast)12. Mycoplama sp.
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