Normal flora, including bacteria, fungi and viruses, colonize various sites of the human body through mutualistic and commensal relationships. Microbiota commonly reside on the skin, in the mouth, respiratory tract, gastrointestinal tract, eyes, and genital region through tissue specificity involving bacterial adherence and biofilm formation preferential for certain tissues. While generally beneficial, microbiota can become pathogenic under conditions like immunosuppression or change in location. References included Medical Microbiology and Jawetz Melnick & Adelbergs Medical Microbiology textbooks.

2. * Definition of normal flora
* species of normal flora
* Advantages and disadvantages
* Symbiotic relationship
* Types of normal flora
Resident Flora transient flora
* Tissue Specificity of Normal Flora
1. Tissue tropism
2. Specific adherence
3. Biofilm formation
*Normal Flora and human body
Skin
Eyes (i.e. Conjunctiva)
Oral and Upper Respiratory Tract
Urogenital tract
Gastrointestinal tract and rectum
* Diseases caused by microbiota
* Fungi
* Viruses * Conclusion * References

6. 1.Provide a first line of defense against microbial pathogens
through “bacterial interference”.
interference may involve competition for receptors or
binding sites on host cells, competition for nutrients.

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

9. 5. the microbiota affect carcinogenesis in three broad ways:
(i) altering the balance of tumor cell proliferation and
death.
(ii) regulating immune system function .
(iii) influencing metabolism of host-produced factors, foods
and pharmaceuticals
such as : Lactobacillus and Bifidobacteria, are known to
prevent tumor formation

10. They can cause disease in the
following:
a) When individuals become
immunocompromised.
b) When they change their usual
anatomic location.

11.  1. Mutualistic
 Both organisms benefit – “mutually beneficial”
 Exp: Escherichia coli
 Synthesizes Vitamin K & B complex Vitamins
 In return, we provide a warm, moist nutrient rich
environment for E. coli.
 2. Commensalistic
 One organism benefits, the other is neither helped nor
harmed

12.  3. Opportunistic
 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
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
the upper respiratory tract, but if it gets into a wound
or a burn it can become pathogenic.

13.  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

14.  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

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

16. Most members of the normal bacterial flora prefer to
colonize certain tissues and not others. This "tissue
specificity" is usually due to properties of both the host
and the bacterium.
Usually, specific bacteria colonize specific tissues by one
or another of these mechanisms:
1. Tissue tropism
2. Specific adherence
3. Biofilm formation

17. is the bacterial preference for certain tissues for
growth. One explanation for tissue tropism is that the host provides
essential nutrients and growth factors for the bacterium, in addition
to suitable oxygen, pH, and temperature for growth.
Lactobacillus acidophilus, informally known as "Doderlein's bacillus" colonizes the vagina
because glycogen is produced which provides the bacteria with a source of sugar that they
ferment to lactic acid.

18. Most bacteria can colonize in specific tissue
because they can adhere to that tissue in a specific manner that
involves chemical interactions between bacterial surface components
and host cell molecular receptors. The bacterial components are
molecular parts of their capsules, fimbriae, or cell walls. The
receptors on human cells are usually glycoprotein molecules located
on the host cell.

19. Bacterium Bacterial adhesin Attachment site
Streptococcus pyogenes Cell-bound protein (M-
protein)
Pharyngeal epithelium
Streptococcus mutans Cell- bound protein (Glycosyl
transferase)
Pellicle of tooth
Streptococcus salivarius Lipoteichoic acid Buccal epithelium of tongue
Bordetella pertussis Fimbriae ("filamentous
hemagglutinin")
Respiratory epithelium
Vibrio cholerae N-methylphenylalanine pili Intestinal epithelium
Mycoplasma Membrane protein Respiratory epithelium

20. Some of the indigenous bacteria are able to construct biofilms on a
tissue surface, or they are able to colonize a biofilm built by another
bacterial species.
Biofilms usually occur when one bacterial species attaches
specifically or non specifically to a surface, and then secretes
carbohydrate slime that imbeds the bacteria and attracts other
microbes to the biofilm for protection or nutritional advantages.

22. In a healthy human, the internal
tissues such as:
 blood
 brain
 muscle
 crebro spinal fluid (c.sf.)
are normally free of
microorganisms.

23.  Skin
 Eyes (i.e. Conjunctiva)
 Oral and Upper Respiratory Tract
 Urogenital tract
 Gastrointestinal tract and rectum

25. Staphylococcus epidermidis
Staphylococcus aureus (in small numbers)
Micrococcus species
α-Hemolytic and non hemolytic streptococci
(eg, Streptococcus mitis)
Corynebacterium species
Propionibacterium species
Peptostreptococcus species
Acinetobacter species
Small numbers of other organisms (Candida species, Pseudomonas
aeruginosa, etc)

26. Diphtheroids , nonpathogenic Neisseria species, α-
hemolytic streptococci; S epidermidis, non hemolytic streptococci,
anaerobes (too many species to list) Prevotella species, anaerobic
cocci, Fusobacterium species, etc
Lesser amounts of the following when accompanied by organisms
listed above: yeasts, Haemophilus species, pneumococci, S aureus,
gram negative
rods, Neisseria meningitidis

28. Various Enterobacteriaceae except Salmonella, Shigella, Yersinia.
Campylobacter species
Glucose non-fermenting gram-negative rods Enterococci
α-Hemolytic and non hemolytic streptococci
Diphtheroids
Staphylococcus aureus in small numbers
Yeasts in small numbers
Anaerobes in large numbers.

29. Corynebacterium species, Lactobacillus species, α-hemolytic and
nonhemolytic streptococci, nonpathogenic
Neisseria species
enterococci, Enterobacteriaceae and other gram-negative rods,
Staphylococcus epidermidis,
Candida albicans, and other yeasts
Anaerobes (too many to list); : Prevotella, Clostridium, and
Peptostreptococcus species

30. The conjunctiva harbors few or no organisms.
Haemophilus and Staphylococcus are among the genera most often
genera most often detected.

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 infective endocarditis.

32. are the most common resident bacteria of the large intestine
quite harmless in that location. However, if introduced into the
peritoneal cavity or into pelvic tissues along with other bacteria
result of trauma, they cause suppuration and bacteremia

33. Some genera of bacteria, such as : Bacteroides and Clostridium ,
have been associated with an increase in tumor growth rate.

35. Fungi, in particular yeasts , are present in the human gut.
The best-studied of these are candida species due to their ability to
become pathogenic in immunocompromised and even in healthy
hosts Yeasts are also present on the skin , such as malassezia species,
where they consume oils secreted from the sebaceous gland.

36. Viruses, especially bacterial viruses (bacteriophages), colonize
various body sites. These colonized sites include the
skin, gut, lungs, and oral cavity. Virus communities have been
associated with some diseases, and do not simply reflect the
bacterial communities.

37. *Normal flora (microbiota) colonize in human bodies since birth until death , some
species are benefit to human such as : defense against pathogens , produce
vitamin K and B ,which known as “mutualistic”.
*In certain situations may become pathogen especially when change normal
region or immunosuppression “opportunistic” .
*Microbiota consists of bacteria , fungi and viruses and the common sites where
colonize are skin, mouth , respiratory tract, gastrointestinal tract , eye and genital.
*Some regions are sterile (no microbiota) which are blood , brain , muscle and CSF.
*Tissue specificity" is usually due to properties of both the host and the bacterium.

38. :
* Medical Microbiology, 4th edition , Samuel Baron.
*Jawetz Melnick&Adelbergs Medical Microbiology ,
26thedition , Janet Butel and Karen C. Carroll