A brief explanation of Normal Microbial flora in the human body - 2021. For Scientific Free Lectures, Visit - http://bit.ly/VisitZofirAcademy

1. ARMAN FIROZ
PhD Scholar
School of BioSciences and Technology
VIT University, Vellore- 632014
NORMAL HUMAN
FLORA

2. The human microbiome (or human microbiota) is the aggregate
of microorganisms that reside on the surface and in deep layers
of skin, in the saliva and oral mucosa, in the conjunctiva, and in
the gastrointestinal tracts. They include bacteria, fungi. Some
of these organisms perform tasks that are useful for the human
host. However, the majority have no known beneficial or
harmful effect. Those that are expected to be present, and that
under normal circumstances do not cause disease, but instead
participate in maintaining health, are deemed members of the
normal flora
HUMAN MICROBIOME

3. NORMAL BACTERIAL FLORA
More bacteria than human cells in the body
• provide some nutrients (vitamin K)
• stimulate immune system, immunity can be cross-reactive against
certain pathogens
• Prevent colonization by potential pathogens (antibiotic-associated
colitis, Clostridiumdifficile)
OVERVIEW OF HUMAN-MICROBIAL INTERACTIONS
❑ The reasons for understanding the normal flora of the healthy human body
❖ Normal flora vs. human body
❖ Some normal flora:
o opportunistic pathogens
o when injury occurred,
o when resistance of body decreased,
o when moved to another site
❑ Origin of the normal flora
❑ Relationship between normal flora and
human host
❑ Distribution and occurrence of the normal
flora

4. WHERE TO FIND MICROBE?
EVERYWHERE!

5. Opportunistic
Commensalistic
SYMBIOTIC
RELATIONSHIP
Mutualistic
SYMBIOSIS

6. Mutualistic Commensalistic Opportunistic
● Both organisms benefit –
“mutually benefical”
● Escherichia coli
● Synthesizes Vitamin K
& B complex
Vitamins
● In return, we provide a
warm, moist nutrient
rich environment for
E. coli
● One organism
benefits, the other is
neither helped nor
harmed
● 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.
• Under normal conditions,
microbe does not cause
disease, but if conditions
become conducive , it can
cause disease.
• 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

7. FACTORS INFLUENCING NORMAL FLORA
Diet
Health condition
(immune activity)
Antibiotics
Local Environment
(pH, temperature,
redox potential, O2,
H2O, and nutrient
levels…).

8. Resident Flora
● Microbes that
are always
present
Transient Flora
● Microbes that
live in or on
your body for
a period of time
(hours, days,
weeks, months)
then move on or
die off
They constitute a protective host defense mechanism by
occupying ecological niches.

9. SITES THAT HARBOR A NORMAL FLORA:
Sterile tissues o Skin
o Eyes (i.e.Cunjunctiva)
o Nose (i.e. Respiratory tract)
o Mouth (i.e Human Oral Cavity)
o Ears
o Urogenetal tract Elementry tract
In a healthy human, the internal tissues such as:
o Blood
o Brain
o Muscle
o Cerbrospinal fluid (csf.) Are normally free of
microorganisms.
Mouth ; > 600 Species
Skin : > 600 Species
Intestine : (Cecum/ colon) : 8,000 genera
Vagina : > 200 Species
HOW MANY DIFFERENT ORGANISMS ARE NORMALLYIN OUR BODY?

10. Yes
How?
No
Why ?
❑Microbes can communicate each other by chemical language
❑They interact each other by signals and respond to the signals by
using chemical language
❑This Phenomenon is called “ Quorum Sensing”
❑Quorum Sensing signals are called auto inducers
❑All auto inducers are chemical language signals to one another.
❑Quorum Sensing is a system of stimulus and response correlated
to population density. Many species of bacteria use quorum
sensing to coordinate gene expression according to the density of
their local population.

12. WHAT DO THE MICROBES DO FOR US?
❑ Provide the ability to harvest
nutrients and Produce
additional energy otherwise
inaccessible to the host.
❑ Produce vitamins
❑ Metabolize xenobiotics
❑ Provide resistance to tumor
and cancer leading neoplasms
❑ Assist in developing a mature
immune system.
Microbialcommunityinthegut
How does community composition affect function?

13. INTESTINAL MICROBIOME
❑ >1,000 species but most in adults are from 2 phyla: Firmicutes and
Bacteroidetes
❑ Outnumber human somatic cells by factor of 102
❑ Total Weight: 1-2 kg
❑ 60% of total fecal content
❑ Concentration: ~1012/gram in colon
❑ Total #: ~1014

14. NORMAL FLORA OF THE RESPIRATORY TRACT
A) The nares (nostrils)
1.Staphylococcus epidermidis
2.Corynebacterium
3.Staphylococcus aureus
4.Neisseria sp.
5.Haemophilus sp
6.Streptococcus pneumoniae
B) The upper respiratory
tract (nasopharynx).
1.Non-hemolytic streptococci
2.Alpha-hemolytic streptococci
3.Neisseria sp.
4.Streptococcus pneumoniae
5.Streptococcus pyogenes
6.Hemophilus influenzae
7.Neisseria meningitidis
•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)

15. 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.

16. METABOLOMICS
•Study of the metabolites and small
molecules that the body and gut bacteria
produce.
•New area of science
•Broader than proteomics
•Includes bacteria products with our own
genetic products
•Pioneered by Jeremy Nicholson and Jeff
Gordon
•Microbial genomes enhance our
metabolic activity
•May indirectly or directly affect our
metabolism
•The colon is very active metabolically
•20-70 gms of carbons and 5-20 gms of
protein/day
•Over 100 kcal per day!
•Mass of colonic microbiome = single
kidney
•Metabolically as active as the liver

17. FECAL MICROBIOTA TRANSPLANTS [FMT]
Fecal microbiota transplantation (FMT) also known as a
stool transplant is the process of transplantation of fecal
bacteria from a healthy individual into a recipient.
❑Clostridium difficile also known as "CDF/cdf", or "C.
diff", is a species of Gram-positive spore-forming
bacterium that is best known for causing antibiotic-
associated diarrhea(AAD).
❑While it can be a minor normal component of colonic
flora, the bacterium is thought to cause disease when
competing bacteria in the gut have been wiped out by
antibiotic treatment.
❑In severe cases, C. difficile can cause
"pseudomembranous colitis," a severe inflammation of the
colon.
PROCEDURE
❑Donar History(Similar to blood
donation)
❑Obtain stool sample,
homogenize with saline and filter
❑How to Administer
❑Nasogastric Tube
❑Enema
❑Colonoscope
❑Perform 6-24 hrs of obtaining
the sample
❑Future:Frozen Samples,
Lyophilized Powders,Capsules.?

18. BACTERIOTHERAPY
Clostridium difficile-associated diarrhea (CDAD)
-usually results from prior antibiotic treatment and persistent disruption of gut microbiota
-can be severe, even causing death
J Clin Gastroenterology (2010) 44:354-360

19. CONCLUSIONS
❏ The human microbiome and the Microbiome Project: research just beginning…
❏ Gut flora by their genes, by-products, and metabolic activity influence our metabolism,
weight, activity, immunity, health and disease.
❏ Manipulation of gut flora may be an integral part of weight loss programs and different
disease treatments in the future.
❏ Future studies must focus on the mechanisms that influence of our gut flora.
❏ Studies must be place to controlled and high quality research should be done.
❏ Truly need translational science to work at the levels of the petri dish, genomics, and
clinical outcomes.
❏ Hope much much more to come!