Role and Importance of Normal flora in Different Parts of Body

The 'normal microflora' is the term most commonly used when referring to the microbial collection that consistently inhabits the bodies of healthy animals. Other terms used are 'normal flora', 'commensals' and 'indigenous microbiota'.

2. Their flourishing depends on physiological factors of
temperature, moisture, and presence of certain nutrients
Species of normal flora
1.Bacteria
2.2. Fungi

3. 1.Provide a first line of defense against microbial pathogens
through “bacterialinterference”.
Interference may involve competition for receptors or
binding sites on host cells, competition fornutrients.

4. 2. Assist in digestion: They produce vitamin B and vitamin K in
intestine.
3.Play a role in toxindegradation
4.The oral flora contribute to immunity by inducing low levels of
circulating and secretory antibodies that may cross react with
pathogens.

5. 5.The microbiota affect carcinogenesis in three broadways:
(i)Altering the balance of tumor cell proliferation and
death.
(ii)Regulating immune system function.
(iii)Influencing metabolism of host-produced factors, foods and
pharmaceuticalssuch as : Lactobacillusand Bifidobacteria, are
known to prevent tumorformation

6. Theycancausediseaseinthe following:
a)When individuals becomeimmunocompromised.
b)When they change their usual anatomic location.

7. 1.Mutualistic
Both organisms benefit –“mutuallybeneficial”
Example:Escherichia coli
Synthesizes VitaminK&B complexVitamins
In return, we provide a warm, moist nutrient rich
environmentforE.coli.
2.Commensalistic
One organism benefits, the other is neither helped nor
harmed

8. 3.Opportunistic
Under normal conditions, microbe does not cause
disease, but if conditions become conducive, it can
causedisease.
Escherichiacoli-normally in our digestive tractwhere
it causes no problems, but if it gets into the urinary
tract it can becomepathogenic.
Staphylococcus aureus –commonly found in the upper
respiratory tract, but if it gets into a wound or a burn it
can becomepathogenic.

9. 1. ResidentFlora
Microbes that are alwayspresent
2. TransientFlora
Microbes that live inoronyour body for a period
of time (hours, days, weeks, months) then move
on or dieoff

10. Remain in the body for only hours to months
before disappearing
Found in the same regions as residentmicrobiota
Cannot persist in thebody…because…
Competition from othermicroorganisms
Elimination by the body’s defensescells
Chemical or physical changes in thebody

11. If the resident microbiota is disturbed, transient
microorganisms may colonize, proliferate, and
produce disease.

12. Mostmembersofthenormalbacterialflorapreferto
colonizecertaintissuesandnotothers.This"tissue
specificity"isusuallyduetopropertiesofboththehost
andthebacterium.
Usually,specificbacteriacolonizespecifictissuesby
oneoranotherofthesemechanisms:
1.Tissuetropism
2.Specificadherence
3.Biofilmformation

13. Thebacterialpreferenceforcertaintissuesforgrowth.
Oneexplanationfortissuetropismisthatthehost
providesessentialnutrientsandgrowthfactorsforthe
bacterium,inadditiontosuitableoxygen,pH,and
temperatureforgrowth.

14. Mostbacteriacancolonizeinspecifictissue
becausetheycanadheretothattissueinaspecificmannerthat
involveschemicalinteractionsbetweenbacterialsurfacecomponents
andhostcellmolecularreceptors.
Thebacterialcomponentsaremolecularparts
oftheircapsules,fimbriae,orcellwalls.Thereceptorsonhuman
cellsareusuallyglycoproteinmoleculeslocatedonthehostcell.

15. Someoftheindigenousbacteriaareabletoconstructbiofilms
onatissuesurface,ortheyareabletocolonizeabiofilmbuiltby
anotherbacterialspecies.
Biofilmsusuallyoccurwhenonebacterialspeciesattaches
specificallyornonspecificallytoasurface,andthensecretes
carbohydrateslimethatimbedsthebacteriaandattractsother
microbestothebiofilmforprotectionornutritionaladvantages.

16. In a healthy human, the internal
tissues suchas:
blood
brain
muscle
crebro spinal fluid(C.S.F.)are
normally free of
microorganisms.

17. Skin
Eyes (i.e.Conjunctiva)
Oral and Upper RespiratoryTract
Urogenitaltract
Gastrointestinal tract andrectum

18. Staphylococcus epidermidis
Staphylococcus aureus (in smallnumbers)
Micrococcusspecies
Streptococci (eg, Streptococcusmitis)
Corynebacteriumspecies
Propionibacterium species
Peptostreptococcusspecies
Acinetobacterspecies
Small numbers of other organisms (Candida species, Pseudomonas
aeruginosa,etc)

19. Diphtheroid,nonpathogenicNeisseriaspecies;Sepidermidis.
anaerobes(toomanyspeciestolist)Prevotellaspecies,anaerobic
cocci,Fusobacteriumspecies,etc
Lesseramountsofthefollowing:yeasts,Haemophilusspecies,
pneumococci,Saureus,gramnegativerods,Neisseriameningitis

20. Various Enterobacteriaceae except Salmonella, Shigella, Yersinia.
Campylobacterspecies
Glucose non-fermenting gram-negative rodsEnterococci
α-Hemolytic and non hemolytic streptococci
Diphtheroids
Staphylococcus aureus in small numbers
Yeasts in smallnumbers
Anaerobes in largenumbers.

21. The conjunctiva of the eye has
primarily S. epidermidis, S. aureus, C. diphtheroids, and
S. pneumoniae.
Some skin normal flora are also present but at fewer amounts.
Tears (Lysozymeenzyme), mucus, and oil will protect the
conjunctiva of the eye from colonization by more bacteria.

22. Microflora of the SKIN
▪The resident micofloraof the skin consist primarily
bacteria and fungi
▪Resident bacteria of the skin can be in any layer of
the skin.
▪Skin can acquire any transient bacteria from the
environment but it either get washed off or die
because the skin is dry, has acidic pH, and produce
sweat and oil.

23. SKIN
Aerobic Bacteria:
-Present in the outer layer of skin.
-Staphylococcus epidermidis(accounts 90%) +
Staphylococcus aureus.
Anaerobic Bacteria: (More than Aerobic bacteria)
-Present in the deeper skin layers, hair follicles, and sweat &
sebaceous glands.
-Propionibacterium acne.
Skin normal flora are generally
harmless but it might cause
bloodstream infections if skin
was penetrated.

24. HCWs
HCWs(Healthcareworkers)mustbe
particularlycarfultokeepthereskin
andclothingfreeoftransientmicrobes
aspossibletopreventpersonal
infectionsandtoavoidtransferring
pathogentopatient

25. Microfloraof the EARS
The middle ear and inner ear:
are usually sterile.
The outer ear and the auditory
canal:contain the same
normal flora of the skin.
When the person coughs,
sneezes, or blows his nose,
these microbes may move into
the middle ear where they
cause infection.

26. Respiratory Tract
Upper Respiratory Tract:
-Nose and throat.
Have many microorganisms. Some
are normal flora, some are
opportunistic,
-Nasopharynx:
Streptococcus pneumoniae
In immune compromised or elderly it might cause
acute bacterial pneumonia.
Lower Respiratory Tract:
Is usually sterile because the mucous membranes
of the lungs remove any microbes.

27. Oral Cavity (Mouth)
They have both aerobic
and anaerobic bacteria.
The most common ones are:
S. aureus, S. epidermidis
and Corynebacterium diphtheroids
Also yeasts, molds,
protozoa, and viruses can be living in the mouth.
Teeth and Gengiva:Streptococcusmutans
Poor dental hygiene help bacteria to grow and cause
dental caries, gingivitis,...
After dental surgeries, there might be a risk of
bloodstream infection that might cause endocarditis.

28. Gastrointestinal Tract

29. Microflora of the Gastrointestinal Tract
Stomach:
Onlyfewbacteriaarepresentinthestomachduetogastricenzymesand
acidicpH.
Smallintestine:
Onlyfewnormalfloraarepresentintheupperpartofsmallintestine
becausebilekillsthem.Lowerpartshavemoreno.ofnormalflora.
Largeintestine:
✓Hasmorebacteriathananyotherpartofthebody.
✓99%ofnormalflorainthelargeintestineareanaerobicBacteroidesspp.
(Bacteroidesovatus,Bacteroidesthetaiotaomicron,Bacteroides
distasonis),andBacteroidesvulgatus)
✓Manyfungi,protozoa,andvirusescanlivethere.
✓Manyofthenormalfloraareopportunistici.e.iftheymovetootherareas
e.g.E.colicauseurinaryinfection.

30. Microfloraof the Urogenital Tract
Urinary Tract
Kidneys, Ureters and Urinary Bladder:are sterile.
Lower Urethra and external opening:bacteria,
yeast, and viruses & the same bacteria present on
the skin.
Genital Organs
Male and female genitals: are sterile except
vagina.
Vagina:Lactobacillus spp.keeps the pH acidic to
protect the vagina from opportunistic infections

31. For example, streptococci of the viridans group are the
most common resident organisms of the upper
respiratory tract.
If large numbers of them are introduced into the
bloodstream (eg, after tooth extraction or oral
surgery), they may settle on deformed or prosthetic
heart valves and produce infectiveendocarditis.

32. Themostcommon residentbacteriaofthe
largeintestinequiteharmlessinthatlocation.
However,ifintroducedintotheperitoneal
cavityorintopelvictissuesalongwithother
bacteria resultoftrauma,theycause
suppurationandbacteremia

33. Fungi,inparticularyeasts,arepresentinthehumangut.
Thebest-studiedofthesearecandidaspeciesduetotheirability
tobecomepathogenicinimmunocompromisedandeveninhealthy
hosts.
Yeastsarealsopresentontheskin,suchasmalasseziaspecies,
wheretheyconsumeoilssecretedfromthesebaceousgland.

34. Beneficial Functions of Normal Flora
1.Protect our organs and systems that are in
direct contact with the external environment
from invading pathogens. Some normal flora
produce substances that kills pathogens and
others compete for with them for nutrients.
2.In newborns, normal flora stimulates the
development of immune system.
3.Normal flora of the gut provides important
nutrients such as Vitamin K which aid in
digestion and absorption of nutrients.

35. Harmful Effect of Normal Flora
1.When the normal flora are displaced from their normal site of
the body e.g.bloodstream infections by S. epidermidis.
2.When potential pathogens gain a competitive advantage
due to reduced populations of harmless competitors e.g.
Clostridioidesdifficile growing in the gut after antibiotic
therapy.
3.When harmless, commonly ingested food substances are
converted into carcinogenic derivatives by bacteria in the
colon e.g.sweetener cyclamate.
4.When individuals are immunocompromised , normal flora can
overgrow and become pathogenic.