1. مايكرو نظري / ثالث اسنان كركوك د. زبيدة 2016/12/27
NORMAL Oral FLORA

2. WHAT IS NORMAL MICROFLORA
is the aggregate of microorganism that reside on the surface and in deep layers of skin, in the saliva and oral mucosa, in the conjuctiva, and in the gastrointestinal tracts.’
Normal Flora absent in Sterile tissues
In a healthy human, the internal tissues such as:
• blood
• brain
• muscle
• cerbrospinal fluid (csf.)
are normally free of microorganism
oral microflora
The microflora existing in the oral cavity is called as oral microflora.

3. NORMAL FLORA ARE MUTUALISTIC
Both host and bacteria are thought to derive benefit from each other, and the associations are, for the most part, mutualistic.
The normal flora derive from their host a steady supply of nutrients, a stable environment, and protection and transport.
The host obtains from the normal flora certain nutritional and digestive benefits, stimulation of the development and activity of immune system, and protection against colonization and infection by pathogenic microbes

4. The normal flora protect us from disease by

6. THE ORAL MICROFLORA IN HEALTH AND DISEAS
The mouth is similar to other sites in the body in having a natural microflora with a characteristic composition and existing, for the most part, in a harmonious relationship with the host

8. The Composition of Normal flora
The makeup of the normal flora influenced
genetics
age
sex
stress
nutrition
and diet of the individual.

9. his relationship can break down in the mouth and disease can occur
his relationship can break down in the mouth and disease can occur. This is usually associated with: 1- major changes to the biology of the mouth from exogenous sources (examples include: antibiotic treatment or the frequent intake of fermentable carbohydrates in the diet) or from endogenous changes such as alterations in the integrity of the host defences following drug therapy, which perturb the natural stability of the microflora

10. Bacteria with the potential to cause disease in this way are termed ‘opportunistic pathogens’ disease in the mouth caused by imbalances in the composition of their resident oral microflora. The commonest clinical manifestations of such imbalances are dental caries and periodontal diseases

11. Dental caries:- is the dissolution of enamel or root surfaces (demineralization) by acid produced primarily from the metabolism of fermentable carbohydrates in the diet by bacteria colonizing the tooth surface (dental plaque). Dental plaque is also associated with the etiology of periodontal diseases in which the host mounts an inappropriate inflammatory response to an increased microbial load (due to plaque accumulation) around the gingivae, resulting in damage to the supporting tissues of the teeth

12. MICROBIAL ECOLOGY
Most diseases of the mouth have a polymicrobial (multiple species) etiology. The ability of consortia of bacteria to cause disease depends on the outcome of various interactions both among the microbes themselves, and between these microorganisms and the host

13. The composition and metabolism of bacteria at a site will be influenced by the 1- flow rate and properties of saliva 2- the life-style of an individual (in particular, the presence of a tobacco habit, the nature of the diet, and exposure to medication) 3- the integrity of the host defences. 4- Oral microflora

14. The inter-relationships that influence the microbial ecology of the mouth in health and disease. The predominant microorganisms in the mouth might alter due to changes in saliva flow, life-style (e.g. tobacco habit, diet) or to changes in the integrity of the host defences. These changes may predispose sites to diseas

15. THE MOUTH AS A MICROBIAL Sites and factors))HABITAT
1-Mucosal surfaces The mouth is similar to other ecosystems in the digestive tract in having mucosal surfaces for microbial colonization. The microbial load is relatively low on such surfaces due to desquamation. The papillary structure of the dorsum of the tongue provides refuge for many microorganisms which would otherwise be removed by mastication and the flow of saliva.

17. The tongue can also have a low redox potential
The tongue can also have a low redox potential. which enable obligately anaerobic bacteria to grow.
The tongue can act as a reservoir for some of the Gram negative anaerobes that are implicated in the etiology of periodontal diseases , which may influence the intra-oral distribution of some microorganism, which will in turn influence the composition of the resident microbial community at a site.

18. 2- Teeth
Teeth (and dentures) allow the accumulation of large masses of microorganism and their extracellular products, termed dental plaque. Plaque is an example of a biofilm, also associated with dental caries and periodontal disease.

20. Teeth do not provide a uniform habitat but possess several distinct surfaces due to the physical nature of the particular surface and the resulting different biological properties of the area. e.g. The stagnant areas between adjacent teeth ( approximal) and in the gingival crevice afford most protection to colonizing microorganisms from the adverse conditions in the mouth. Both sites are also anaerobic and, in addition, the gingival crevice region is bathed in the nutritionally-rich gingival crevicular fluid GCF

21. Smooth surfaces of teeth are more exposed to the environment and can only be colonized by a limited number of bacterial species adapted to such extreme conditions. The properties of a smooth surface will differ according to whether it faces the cheek (buccal surface) or the inside (lingual surface) of the mouth

22. Pits and fissures of the biting (occlusal) surfaces of the teeth also offer protection from oral removal forces such as saliva flow, and can contain impacted food debris. Such protected areas are associated with the largest microbial communities and, in general, the most disease.

23. Saliva
Saliva plays a major role in maintaining the integrity of teeth by clearing food and by buffering the potentially damaging acids produced by dental plaque following the metabolism of dietary carbohydrates. Bicarbonate is the major buffering system in saliva, but phosphates, peptides and proteins are also involved. The mean pH of saliva is between pH 6.75 and 7.25, the pH and buffering capacity will vary with the flow rate. The slowest flow of saliva occurring during sleep

24. Temperature
temperature of mouth (35–36°C) which provides stable conditions suitable for the growth of a wide range of microorganisms., with active disease (inflammation) have a higher temperature(up to 39°C) compared with healthy sites. Even such relatively small rises in temperature can significantly alter bacterial gene expression in periodontal pathogens, such as Porphyromonas gingivalis.

25. Oxygen tension :
The oxygen concentrations at different locations in the oral cavity vary widely.
As may be expected, the dorsum of the tongue and the buccal and palatal mucosa are in an essentially aerobic environment.
The oxygen tension inside a periodontal pocket is very low, with the species having a tendency to become reduced rather than oxidised, explaining the survival of obligate anaerobe.
Therefore obligate aerobic organisms (which require oxygen) cannot survive, whereas obligate anaerobic organisms (which cannot tolerate the presence of oxygen) are able to thrive.

26. pH
Many microorganisms require a pH around neutrality for growth, and are sensitive to extremes of acid or alkali. The pH of most surfaces of the mouth is regulated by saliva (the mean pH for saliva is between 6.75 and 7.25)

27. Nutrients
(i) Endogenous nutrients The main source of endogenous nutrients is 1- Saliva, which contains amino acids, peptides, proteins and glycoproteins (which also act as a source of sugars and amino-sugars), vitamins and gases. 2- Delivering components of the host defences, contains novel nutrients, such as albumin and other host proteins and glycoproteins, including haemecontaining molecules

28. (ii) Exogenous (dietary) nutrients
Ii-1 - fermentable carbohydrates are the only class of compound that markedly influence the ecology of the mouth(Increased the acidity ) The frequent consumption of dietary carbohydrates is associated with a shift in the proportions of the microflora of dental plaque. e.g. The levels of acid-tolerating species, especially mutans streptococci and lactobacilli, increase while the growth of acid-sensitive species (for example, some strains of Streptococcus sanguinis and S. gordonii) is inhibited, and they decrease.

29. Ii-2- -Dairy products (milk, cheese)
The ingestion of milk or milk products can protect the teeth against caries. This may be due to the buffering capacity of milk proteins or due to decarboxylation of amino acids after proteolysis since several bacterial species can metabolise casein. Milk proteins and casein can also adsorb on to the tooth surface, in exchange for albumin in the enamel pellicle, and reduce the adhesion of S. mutans Cheese has been shown to increase salivary flow rates and elevate plaque pH changes following a sucrose rinse

30. Ii-4-Nitrate in green
vegetables may influence the oral microflora. Nitrate derived from the diet is concentrated by salivary glands so that salivary concentrations are higher than plasma. This nitrate can be rapidly converted to nitrite by bacterial nitrate reductases. At low pH, this acidified nitrite can be inhibitory to the growth of bacteria both caries and periodontal diseases.

31. Host defences

32. Host factors : Saliva Crevicular fluid Saliva :
Various salivary components interact with oral flora in ways that can either enhance or inhibit ability of these organisms to survive.
IgG is seen in gingival inflammation contributed by GCF.
These make it more difficult for bacteria to bind to oral epithelium or hard tissue surfaces.

33. Non-specific factors:
These are lysozyme, lactoferrin and lactoperoxidase.
Lysozyme degrades bacterial peptidoglycan i.e the cell wall, rendering bacteria susceptible to osmotic disruption and death.
Lactoferrin binds to iron which is a growth limiting substance in bacteria. Making iron unavailable to bacteria lactoferrin limits bacterial growth.
Lactoperoxidase catalyses the formation of hypothiocyanate ion ,inactivating bacterial enzymes and finally death.

34. 2. Crevicular fluid :
It is an inflammatory exudate derived from plasma with large amount of antibody and complement proteins.
The predominant immunoglobulin is IgG, derived from plasma cells located in periodontal tissues as well as from circulating plasma.
These antibodies keep the subgingival flora in check by inhibiting colonization or activating complement system.

35. (ii) Adaptive immunity
Components of the specific host defences (intraepithelial lymphocytes and immunoglobulins IgG and IgA) are found on and within the mucosa where they act as a barrier to penetrating antigens.

39. Important Oral Bacteria
I1. Gram Positive organisms: • Bulk of oral bacteria • Rods (bacilli), cocci or irregular shape (pleomorphic) • Oxygen tolerance varies from aerobes to strict anaerobes • Most are fermentative • Three important genera: • Actinomyces, facultative anaerobe • Lactobacillus, produce lactic acid, facultative anaerobe, role in dentine caries rather than enamel caries • Streptococcus facultative anaerobic cocci, produce lactic acid some implicated in caries

40. Streptococci: • Associated with bacterial endocarditis • Isolated from all sights of the mouth • Large proportion of resident microflora • Majority α-haemolytic Strep mutans: • Associated with caries Strep salivarius: • Colonise mucosal surfaces especially the tongue Strep angiosus: • Isolated dental plaque & mucosal surfaces • Seen in maxillofacial infections, brain, liver etc Strep mitis: • Opportunistic pathogens e.g. endocarditis

41. Actinomyces: • Short pleomorphic rods with branching • Major proportion of plaque • Increase in gingivitis • Associated with root caries

42. Important Oral Bacteria
Gram Negative organisms
Many Gram-negative bacteria found in the mouth, especially in established/subgingival plaque
Cocci, rods, filamantous rods, spindle shaped or spiral shaped
Range of oxygen tolerance but most important strict or facultative anaerobes Some fermentative, produce acids which other organisms use acids as an energy source, others produce enzymes which break down tissue

43. Most important Gram negative bacteria:
Porphyromonas: P. gingivalis major periodontal pathogen • Prevotella: P. intermedia a periodontal pathogen • Fusobacterium: F. nucleatum periodontal pathogen • Actinobacillus/ associated with aggressive periodontitis •Treponema: group important in acute periodontal conditions • Neisseria • Veillonella

44. Some definition for medical Terminologies
Habitat: the site where a microorganism grows
Ecology: Study of relationship between organisms and their environment.
Ecological niche: The functional position of an organism in its environment comprising the living space, periods of time during which it is active there and resources it obtains there.

45. Indigenous Flora(Resident):
It comprises those indigenous species that are almost always present in high numbers, greater than 1 % of the total viable count.
Supplemental Flora:
The supplemental flora are those bacterial species that are nearly always present, but in low numbers, less than 1 % of total viable count
Transient Flora:
Transient flora comprise organisms "just passing through" a host. At any given time a particular species may or may not be represented in the flora.

46. Pathogens
Micro­organisms that have the potential to cause disease are termed pathogens.
Opportunistic Pathogens
Micro-organisms that cause disease only under exceptional circumstances .
True Pathogens
Micro-organisms that are consistently associated with a particular disease .