1. Microbial Flora of the Human Body
Dr. Rashad Shawgi Babiker
M.Sc (Microbiology) (UMST)
M.Sc. Stud. (Immunology )
Institute of Tropical Medicine.(SAS)

2. Normal Flora Definition
Normal flora is the mixture of microorganisms (bacteria and fungi) that are regularly found at any anatomical site of human body.

4. Symbiotic Relationship
1. Mutualistic
Both organisms benefit – “mutually benefical”
2. Commensalistic
One organism benefits, the other is neither helped nor harmed
3. Opportunistic
Under normal conditions, microbe does not cause disease, but if conditions become conducive , it can cause disease

5. Mutualistic Escherichia coli
Synthesizes Vitamin K & B complex Vitamins
In return, we provide a warm, moist nutrient rich environment for E. coli

6. 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.

7. 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

8. The Three Types of Symbiotic Relationships
Table 14.1

9. Normal Microbial Flora
1. Resident Flora
Microbes that are always present
2. 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

11. Transient Microbiota
Remain in the body for only hours to months before disappearing
Found in the same regions as resident microbiota
Cannot persist in the body…because…
Competition from other microorganisms
Elimination by the body’s defenses cells
Chemical or physical changes in the body

12. Normal Flora Sterile tissues
In a healthy human, the internal tissues such as:
blood
brain
muscle
cerbrospinal fluid (csf.)
are normally free of microorganisms.

13. Normal Flora Skin Eyes (i.e.Cunjunctiva) Nose (i.e. Respiratory tract)
Mouth (i.e Human Oral Cavity)
Ears
Urogenetal tract
Elementry tract

14. Normal Flora
Resident flora
Acquired rapidly during & after birth

15. Normal Flora
Resident flora
Reflects age of person

16. Normal Flora
Resident flora
Changes continuously through out life .

17. Normal Flora
Resident flora
Reflects nutrition of person

18. Normal Flora
Resident flora
Reflects genetics of person

19. Normal Flora
Resident flora
Reflects environment of person

20. Normal Flora
Resident flora
Reflects sex of person

21. Importance of The Normal Flora (Advantages)
1. They constitute a protective host defense mechanism
by occupying ecological niches.

22. Importance of The Normal Flora (Advantages)
2. They produce vitamin B and vitamin K in intestine.

23. 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.

24. Importance of The Normal Flora (Advantages)
5. The normal flora may antagonize other bacteria through the production of substances which inhibit or kill nonindigenous species.

25. Importance of The Normal Flora (Disadvantages)
1. They can cause disease in the following:
a) When individuals become immunocompromised.
b) When they change their usual anatomic location.

26. Importance of The Normal Flora
2. The oral flora of humans may harm their host since some of these bacteria are pathogens or opportunistic pathogens

27. Contamination vs. Infection
Contamination – the mere presence of microbes in or on the body
Infection – results when the organism has evaded the body’s external defenses, multiplied, and become established in the body

28. Portals of Entry Sites through which pathogens enter the body
Four major types
Skin
Mucous membranes
Placenta
Parenteral route

29. Skin
Outer layer of packed, dead, skin cells usually acts as a barrier to pathogens
Some pathogens can enter through openings or cuts
Others enter by burrowing into or digesting the outer layers of skin…flesh-eating bacteria

30. Mucous Membranes
Line the body cavities that are open to the environment
Provides a moist, warm environment that is hospitable to pathogens
Respiratory tract is the most commonly used site of entry – entry is through the nose, mouth or eyes
Pathogens able to survive the acidic pH of the stomach may use the gastrointestinal tract as a route of entry

31. Some Pathogens that Cross the Placenta
Table 14.3

32. Parenteral Route
Pathogens deposited directly into tissues beneath the skin or mucous membranes

33. Infection vs. Disease
Infection is the invasion of the host by a pathogen
Disease results only if the invading pathogen alters the normal functions of the body
Disease is also referred to as morbidity

34. Manifestations of Disease
Symptoms – subjective characteristics of disease felt only by the patient
Signs – objective manifestations of disease that can be observed or measured by others
Syndrome – group of symptoms and signs that characterize a disease or abnormal condition
Asymptomatic, or subclinical, infections lack symptoms but may still have signs of infection

35. Etiology Study of the cause of disease
Germ theory of disease – disease caused by infections of pathogenic microorganisms
Robert Koch developed a set of postulates one must satisfy to prove a particular pathogen causes a particular disease

36. Koch’s Postulates
Figure 14.7