The document discusses the normal microbial flora found on and within the human body of healthy individuals. It describes the various factors that influence the composition of the normal flora and defines resident and transient flora. It then provides details on the normal flora found at different anatomical sites of the body including skin, eyes, nose, mouth, ears, genitourinary and gastrointestinal tracts. It lists examples of common bacterial species found at each site and discusses their roles and benefits in maintaining human health.

1. Microbial Flora of
Human Body
(Normal Flora)

2. NORMAL FLORA:
These are mixture of micro-organisms
regularly found at any anatomical site
on or within the body of a healthy
person.

3. Factors influencing normal flora:
• The makeup of the normal flora depends upon various
factors, including:
– Genetics
– Age
– Sex
– Stress
– Nutrition
– Diet
– Antiobiotic & other drugs

4. Normal Microbial Flora:
• 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. Anatomical sites involved:
• Skin
• Eyes (i.e Conjunctiva)
• Nose (i.e Respiratory tract)
• Mouth (i.e Human Oral Cavity)
• Ears
• Genitourinary tract
• Alimentary canal

6. BACTERIUM TISSUE
Corynebacterium diphtheriae Throat
N.gonorrhoeae Urogenital epithelium
S.mutans Tooth surfaces
S.salivarius Tongue surfaces
E.coli Small intestine epithelium
S. aureus Nasal membranes
S.epidermidis Skin
EXAMPLES OF TISSUE TROPISM OF SOME
BACTERIA ASSOCIATED WITH HUMANS

7. Normal flora of Skin:
Important bacteria:
1.Staphylococcus epidermidis
2. Micrococcus sp.
3. Corynebacterium sp.
4. Mycobacterium smegmatis

8. Normal Flora of the Conjunctiva:
1. Staphylococcus epidermidis
2. Corynebacterium spp.
3. Propoinibacterium acnes
4. Staphylococcus aureus
5. Viridans streptococci
6. Neisseria spp.
7. Haemophilus influenzae

9. Normal Flora of the Respiratory Tract:
A). The nares (nostrils) :
1. Staphylococcus epidermidis
2. Corynebacteria spp.
3. Staphylococcus aureus
4. Neisseria spp.
5. Haemophilus spp.
6. Streptococcus pneumoniae

10. Normal Flora of the Respiratory Tract:
B) The upper respiratory tract (nasopharynx):
1. Non-hemolytic streptococci
2. Alpha-hemolytic streptococci
3. Neisseria spp.
4. Streptococcus pneumoniae
5. Streptococcus pyogenes
6. Haemophilus influenzae
7. Neisseria meningitidis

11. Normal Flora of the Respiratory Tract:
C) The lower respiratory tract:(trachea, bronchi, and
pulmonary tissues):
• Usually sterile.
• The individual may become susceptible to infection by
pathogens descending from the nasopharynx:
e.g. H. influenzae,
S. pneumoniae

12. Sputum Sample

13. Normal Flora of the Human Oral Cavity:
Oral bacteria include:
1. Viridans streptococci
2. Lactobacilli
3. Staphylococci (S. aureus and S. epidermidis)
4. Corynebacterium sp.
5. Bacteroides sp.
6. Streptococcus sanguis (dental plaque)
7. Streptococcus mutans (dental plaque)
8. Actinomyces sp.

14. The Normal Flora of The Ears (i.e. external ear)
The external ears contains a variety of micro-
organisms. These include:
1. Staphylococcus epidermidis
2. Staphylococcus aureus
3. Corynebacterium sp

15. Normal flora of the Urogenital Tract:
a) The anterior urethra:
1. Staphylococcus epidermidis
2. Enterococcus faecalis
3. Alpha-hemolytic streptococci.
4. Some enteric bacteria (e.g. E. coli, Proteus sp.)
5. Corynebacteria sp.
6. Acinetobacter sp.
7. Mycoplasma sp.
8. Candida sp.
9. Mycobacterium smegmatis

16. Normal flora of the Urogenital Tract:
b) The vagina:
1. Corynebacterium sp.
2. Staphylococci
3. Non-pyogenic streptococci
4. Escherichia coli
5. Lactobacillus acidophilus*
6. Flavobacterium sp.
7. Clostridium sp.
8. Viridans streptococci
9. Other Enterobacteria

17. Vaginal Flora:

18. Urethritis:

19. Normal flora - Gastrointestinal tract
Location (adult) Bacteria/gr
am contents
Duodenum 103
-106
Jejunum and ileum 105
-108
Caecum and
transverse colon
108
-1010
Sigmoid colon and
rectum
1011

20. Normal Flora of the Gastrointestinal Tract
(GIT):
• In breast-fed infants :
1. Bifido bacteria account for more than 90% of the total
intestinal bacteria.
2. Enterobacteriaceae
3. Enterococci
4. Bacteroides
5. Staphylococci
6. Lactobacilli
7. Clostridia

21. 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. Enterics
2. Bacteroides
3. Enterococci
4. Lactobacilli
5. Clostridia

22. Normal Flora of the Gastrointestinal Tract
(GIT):
In the upper GIT of adult humans mainly acid-
tolerant lactobacilli present:
e.g. Helicobacter pylori

23. Normal Flora of the Gastrointestinal Tract
(GIT):
• The proximal small intestine:
1. Lactobacilli
2. Enterococcus faecalis
3. Coliforms
4. Bacteroides

24. The flora of the large intestine (colon):
1. Enterococci
2. Clostridia
3. Lactobacilli
4. Bacteroides
5. Bifidobacterium (Bifidobacterium bifidum)
6. Escherichia coli
7. Methanogenic bacteria
8. Viridans streptococci
9. Staphylococcus sp.
10. Proteus sp.
11. Candida albicans (Yeast)
12. Mycoplama sp.

25. THE ROLE/ BENEFITS OF THE NORMAL FLORA:
1. The normal flora synthesize and excrete vitamins
in excess of their own needs, which can be
absorbed as nutrients by the host.
For example, enteric bacteria secrete Vitamin K
and Vitamin B12, and lactic acid bacteria
produce certain B-vitamins.

26. THE ROLE/ BENEFITS OF THE NORMAL FLORA:
2. The normal flora prevent colonization by
pathogens by competing for attachment sites or
for essential nutrients.
This important beneficial effect, which has been
demonstrated in the oral cavity, the intestine, the
skin, and the vaginal epithelium.

27. THE ROLE/ BENEFITS OF THE NORMAL FLORA:
3. The normal flora may antagonize other bacteria
through the production of substances which
inhibit or kill non-indigenous species.
Intestinal bacteria produce a variety of
substances like non-specific fatty acids, peroxides
and highly specific bacteriocins, which inhibit or
kill other bacteria.

28. THE ROLE/ BENEFITS OF THE NORMAL FLORA:
4. The normal flora stimulates the development of
certain tissues, i.e., the caecum (in animals) and
certain lymphatic tissues (Peyer's patches) in the
GI tract.
The caecum of germ-free animals is enlarged,
thin-walled, and fluid-filled, compared to that
organ in conventional animals.

29. THE ROLE/ BENEFITS OF THE NORMAL FLORA:
5. The normal flora stimulates the production of
“cross-reactive antibodies’’.
Since the normal flora behave as antigens in an
animal, they induce an Ab mediated immune
response.
Low levels of antibodies produced against
components of the normal flora are known to
cross react with certain related pathogens, and
thereby prevent infection or invasion.

30. Sterile tissues:
In a healthy human, the internal tissues
such as:
• blood
• brain
• muscle
• Cerebrospinal fluid (CSF)
are normally free of microorganisms.

31. Role of Microbiologist:
Accurate diagnosis: by Rapid/ quick, meaningful
reporting
Role of Physician:
Proper treatment with antimicrobial regimen/
standard guidelines
by avoiding overuse*/ misuse of antimicrobials
* by treating pathogen, NOT the normal flora!!

32. NATURAL MICROBIAL HABITATS
Soil
Water
Air
Animals and Animal Products

33. PATHOGEN ENVIRONMENT
HOST
DISEASE
TRIAD
Host-Parasite
Interactions
OTHER MICROBES
Microbial Interactions

34. Symbiotic Relationship:
• Mutualistic/ mutualism:
– Both organisms benefit – “mutually benefical”
• Commensalistic/ commensalism:
– One organism benefits, the other is neither helped
nor harmed
• Opportunistic: Under normal conditions, microbe does
not cause disease, but if conditions become conducive ,
it can cause disease. (Immuno-compromised or
immuno-suppressed conditions)

35. Mutualistic
• Escherichia coli :
–Synthesizes Vitamin K & B complex Vitamins
–In return, we provide a warm, moist nutrient
rich environment for Escherichia coli

36. Commensalistic
• We have no Commensalistic relationships with
Bacteria
• If Bacteria are in or on our body, they are either
helping us (Microbial Antagonism) or harming us.

37. Opportunistic:
• Escherichia coli - normally in our digestive tract
where it causes no problems, but if it gets into
the urinary tract it can become pathogenic.
• Staphylococcus aureus – commonly found in the
upper respiratory tract, but if it gets into a
wound or a burn it can become pathogenic

38. Probiotics/ Prebiotics:
• Probiotic:
–Oral administration of living organisms to
promote health
–Species specific: adherence and growth
(tropism)
• Prebiotic: Non-digestible food that stimulates
growth or activity of GI microbiota, especially
bifidobacteria and lactobacillus bacteria
–Typically a carbohydrate: soluble fiber

39. KEY QUESTIONS:
1. Define normal microbial flora. Mention the role/
benefits of normal flora in human body.
2. Normal flora of mouth and upper respiratory
tract.
3. Normal flora of skin.
4. Normal flora of gastro-intestinal tract.
5. Normal flora of genitourinary tract.

40. Nocardia
• Morphologically resembles Actinomyces.
• They are acid fast up to 1% Sulphuric acid.
• Majority of them are saprophytes.
Species:
1.N. asteroides.
2.N. brasiliensis.
3.N. madurae

42. Culture:
Readily grow on ordinary media.
Requires incubation for 3 weeks, usually
produce pigmented colonies.
Pathogenesis:
Mainly produces opportunistic infections in
immuno-compromised persons.
Causes mainly pulmonary disease like
pneumonia, lung abscess or lesion resembling
tubercolosis.
May cause mycetoma.

46. Lab. Diagnosis:
Specimen: Pus or sputum.
Gram’s staining: Gram positive
ZN Staining: Acid fast (1% Sulphuric acid)
Culture:

47. • Treatment:
• MEDICAL Rx- sulfa drugs like TMP-SMX
(Cotrimoxazole) for three months.
• SURGICAL Rx- drainage of abscess

48. THANK YOU