Normal Flora

about normal flora and diseases

1. Normal flora (Microbiota)

2. Contents * 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

3. The term “normal microbial flora ” denotes the population of microorganisms, that inhabit the skin and mucous membranes of healthy normal persons from shortly after birth until death , (now referred to as the normal microbiota ). Definition:

4. Their flourishing depends on physiologic factors of temperature , moisture , and the presence of certain nutrients .

5. Species of normal flora: 1. bacteria. 2. fungi 3. viruses.

6. Advantages 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.

7. 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 . .

8. 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

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

10. Symbiotic Relationship 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

11. 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 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.

12. Types of Normal 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

13. 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

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

15. Tissue Specificity of Normal Flora 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. T issue tropism 2. Specific adherence 3. Biofilm formation

16. 1. Tissue tropism  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.

17. 2. Specific adherence 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.

18. Examples of bacterial specific adherence to host cells or tissue 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 

19. 3. Biofilm formation   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.

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

21. Normal Flora and human body Skin Eyes (i.e. Conjunctiva) Oral and Upper Respiratory Tract Urogenital tract Gastrointestinal tract and rectum

22. Skin 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 )

23. Oral and Upper Respiratory Tract 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

24. Gastrointestinal tract and rectum 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.

25. Genitalia 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

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

27. 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. Diseases caused by microbiota

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

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

30. Fungi 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.

31. Viruses 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 .

32. conclusion *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.

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

34. Thank you Faten matouni