Oral Biology Ii, 9/1/11

Front 1

1. Ecology
2. Ecosystem
3. Habitat
4. Niche

Back 1

Ecology is the study of the interrelationships of organisms and their environment.
Ecosystem is the microbial community in a specific habitat and their abiotic surroundings.
Habitat is the site where organisms grow.
Niche is the function of the organism in a particular habitat. Often misused term.

Front 2

1. Autochtonous/ residence microflora
2. pathogens
3. Oppurtunisitic pathogens

Back 2

Autochtonous or resident microflora refers to those organisms characteristically isolated from a site.
Microorganisms that have the potential to cause disease are termed pathogens
Opportunistic pathogens cause disease under exceptional circumstances

Front 3

3 physiochemical factors in the mouth

Back 3

Temperature: Temperature- influences bacterial metabolism and enzymatic activities.
Temperature of mouth is relatively stable
pH: Organisms each have optimal pH for growth and varying tolerances for extremes of pH.
For example, enhanced growth of acid-tolerant (aciduric) species following frequent carbohydrate exposure.


Oxygen tension

Mouth contrains surprisingly few truly aerobic organisms.
Major oral bacterial species are either facultative anaerobes (can grow with or without oxygen) or obligate anerobes (oxygen is toxic).
A wide spectrum of oxygen tolerance is present among bacteria.


Varies considerably at different sites and under different conditions in the mouth.
For example, falls considerably (+200 Eh; highly oxidized) to - 141Eh (highly reduced) during 7 day plaque development on a clean enamel surface. Also, decreased in the diseased gingival crevice.
These kinds of changes influence ecologic succession during plaque formation.

Front 4

What are components in saliva that make it a good microbial habitat

Back 4

Major organic constituents of saliva are proteins and glycoproteins, e. g. mucins.
These glycoproteins influence:
Aggregation and adhesion of bacteria. Pellicle.
Primary source of nutrients for oral flora.
Concentration of free carbohydrate in saliva is low. Must be derived from metabolism of glycoproteins.


including lyzozyme, lactoferrin, and the sialoperoxidase system.
Antibodies (mostly IgA) also present.
Peptides with specific antimicrobial activity have also been identified.

Front 5

What components in gingival and crevicular fluid make it a good microbial habitat?

Back 5

Serum components reach the mouth by the flow of serum-like fluid through the junctional epithelium of the gingivae.
Flow is quite low in health (0.3 microlliters
/tooth/hour)
Like saliva provides source of nutrients and growth factors. Higher protein concentration than saliva.

phagocytosis in the gingival crevice.
Antibody (mostly IgG) present.
Also contains enzymatic activities of host or bacterial origin associated with pathogenicity. (proteases, collagenases, elastases etc.)


Rise in flow during inflammation leads to increase in pH in gingival crevice. (pH 6.9 (health) to 7.25-8.0 (disease)
This change in pH may influence bacterial populations at these sites.
Also certain bacterial enzymes (proteases) may increase in activity at higher pH

Front 6

What are the principles of microbial taxonomy?

Back 6

Purpose is to develop a logical arrangement of organisms based on their genetic relationships.
Rough estimates of relatedness.
Genotypic vs. Phenotypic
The application of molecular techniques to taxonomy has led to numerous changes

Front 7

Streptococcus

Back 7

Gram-positive cocci
Make up a large percentage of cultivable flora at most oral sites.
Supragingival plaque (28%), Tongue (45%), Saliva (46%) and Subgingival plaque (29%)
Classification at species level is in state of flux.

-isoloated from carious teeth, colonizes it.
-causitive for dental caries.

Front 8

S. Salivarius and S. vestibularis

Back 8

Preferentially colonize the mucosal surfaces.
Not considered opportunistic pathogens.
S. salivarius produces extracellular polysaccharides.

Front 9

Streptococcus milleri

Back 9

Isolated from dental plaque and mucosal surfaces.
Extraoral infections
Three species, S. anginosus, S. constellatus, S. intermedius.

Front 10

Streptococcus oralis group

Back 10

S. gordonii, S. oralis, S. sanguis, S. mitis
Earliest colonizers of the tooth surfaces.
Extraoral infections
Classified on the basis of IgA protease production, neuraminidase production, ability to bind to alpha-amylase and glucan production.

Front 11

Actinomyces

Back 11

Gram-positive rod
Have been associated with gingivitis and root caries.
A. naeslundii, A. israelii, A. odontolyticus, A. viscosus. Taxonomy is in flux.
A. israelii associated with Actinomycosis.

Front 12

1. Lactobacillus
2. Gram Neg cocci
3. Gram neg rods/filaments

Back 12

1. Highly acidogenic and aciduric
Associated with the advancing carious lesion.
3. Fusobacteria, increase in numbers during gingival inflammation.
Bacteroides, Porphyromonas, Prevotella ; anaerobes compose a large percentage of oral flora, particularly at gingival crevice. Many of presumed periodontal pathogens fall into this group.
Also, Wolinella, Selenomonas etc
2. Veillonella spp., anaerobic, do not metablize carbohydrate, metabolize and neutralize lactic acid.
Others, Neisseria

Front 13

What is the initial step in colonization?

Back 13

bacterial adhesion


Involves specific interactions.
Adhesins- bacterial surface structures (proteins) involved in adhesion.
Ligands or receptors- host structures involved in adhesion, often carbohydrates.

Front 14

What are some receptors that are available in the mouth?

Back 14

Epithelial cells of gingival and mucosal tissues.
Other bacterial cells in dental plaque.
Salivary pellicle. Components of saliva that coat the tooth surface.


Many organisms interact with sialic acids, others bind to galactose.
Many interactions of this type were first discovered by hemagglutination.

Front 15

Hemagglutination

Back 15

Many organisms interact with sialic acids, others bind to galactose.
Many interactions of this type were first discovered by hemagglutination.
These are often reversible by a simple sugar = lectin carbohydrate interactions; specific sugrads that block the interaction gives us the identity of the receptor.

Front 16

What is coaggregation

Back 16

-visible agglutination reversed by sugars.
-also have lectin-carbohydrate interactions.

Ex: A. naeslundii T14V and S. oralis 34. inhibited by lactose, galactose and other related sugars.

-C. ochracea and S. oralis H1 inhibited by Rhamnose.

Front 17

What are some receptors in the acquired pellicle?

Back 17

Saliva Coated Hydroxyapatite assay.
Acidic Proline Rich proteins (PRP’s) and statherin. Promote adherence of A. viscosus, Mutans streptococci.
Bacterial glucans in pellicle may also serve as receptor.

Front 18

What are cryptiopes?

Back 18

Certain bacteria only bind to molecules after they are bound to enamel. (Do not bind to soluble forms of PRP)
Receptor molecule undergoes conformational change during adsorption to surface, exposes unique “cryptitopes” for binding.

Front 19

What group for Veillonella coaggregates with S. Sanguis? Which to S. salivarius?

Back 19

Group 1 predominates in dental plaque and dominates in S. sanguis.
Group 2 predominates on mucosal surfaces and interacts with S. salivarius.

Front 20

Are most organisms in the mouth aerobes or anaerobes?

Back 20

Anaerobes predominate
Low O2 due to low saturation content and low diffusion rate of O2 in water.
The little O2 that is available is rapidly depleted by aerobes and facultative anaerobes.


Main energy producing mechanism is fermentation.
Plaque bacteria degrade sugars, amino acids or both.
Relatively low energy yields from fermentation.

Front 21

Describe the nutrients of the oral microflora

Back 21

Saliva, GCF, Desquamated epithelial cells.
Host diet is available at short intervals, only important for limited number of species.

Rich source of Carbohydrate. Most in form of oligosaccharide side chains of glycoproteins.
Mucins and proline-rich glycoproteins account for most of carbohydrate in saliva.
Since most sugars available to oral bacteria are part of oligosaccharide side chains of glycoproteins, glycosidases play a critical role in the ecology of dental plaque.

Front 22

Describe the sugars released and the order in which they are released from the organism as it metabolizes carbs.

Back 22

Sialic acid
Galactose
Fucose

Front 23

What happens if you add sialadase inhibitors to the organism?

Back 23

This stops growth completely since bacteria. Very efficent at getting nutrients from the saliva.
-levels in dental plaque assoc. w/ abilities to grow on mucin.
-also is important in ability of certain organisms to cause extraoral infections.

Front 24

Why aren't mutans streptococci able to grow on mucin?

Back 24

they dont have glycosidase activity and need free carbohydrate to survive.

Front 25

What is adhesion?

Back 25

Ability to bind to host tissues during bacterial infection/invasion an important virulence property of many bacterial pathogens.
Initial stage in infection/Invasion.
Pili, Fimbriae, Liptechoic acid.

plays a role in bacterial endocarditis. fim gene encodes protein invovled in adherence to host by Oral streptococci.

Front 26

What does inactivitation and immunization with FIM a do?

Back 26

Inactivation: reduces virulence in animal endocarditis model

Immunization - protects against endocarditis.

Front 27

Mixed infection models

Back 27

Demonstrate the role that mixed interactions may play in infections.

metabolic interaction play an important role in virulence of oral bacteria.
Tested pathogenic potential of recombined cultures in animal models.
Only specific combinations of organisms will cause infection. Suggest that metabolic consortia are required for many infections.

Front 28

Name the 4 steps in establishment of microbial community

Back 28

1. acquisition/transmission
2. pioneer species
3. ecologic succession
4. climax community

Front 29

What's the first layer of cells in dental plaque known as?

Back 29

condensed microbial layer - layer of dense packed coccoid organisms. 3- 20 layers thick and are early colonizers.

-not metabolizing much, but they may derive nutrients from fluid channels

Front 30

What's the 2nd layer of cells in plaque known as?

Back 30

Body:

Largest portion of plaque
Extremely diverse population of cells
Extracellular matrix

Front 31

3rd layer of plaque?

Back 31

Loosely packed peripheral layer of cells
unusual morphologic arrangements
“corncobs”

Front 32

Steps in plaque formation

Back 32

Pellicle formation
Initial Attachment
Accumulation
Maturation

Front 33

Describe pellicle formation

Back 33

Dental Enamel exhibits more phosphate ions on its outer surface, overall negative charge.
Adsorption of Ca++ ions results in positive charge, following exposure to saliva.


This model would predict that negatively charged, calcium binding molecules would bind preferentially to enamel.

Front 34

What are components of the pellicle?

Back 34

Phosphoproteins
Sulfated glycoproteins
Mucins
Proline rich Proteins
Other acidic proteins of host and bacterial origin
Immunoglobulins

Front 35

Functions of the pellicle?

Back 35

Protects teeth from excessive wear.
Protects teeth from erosion by dietary acids
During plaque formation, provides receptors for bacterial adhesion.

Front 36

Initial attachment

Back 36

Has pioneer species. Mostly Streptococcus spp. (S. oralis, S. gordonii, S. sanguis)
Later Actinomyces, Veillonella, Haemophilus.

-bind to receptors in salivary pellicle
-stuided by spheroidal hydroxyapatite assay

Front 37

Accumulation/ Growth

Back 37

-growth is asynchronous
-early colonizers accumulate.

As receptors in pellicle are occupied, later colonizers bind to other bacteria, pellicle that coats preadherent bacteria and the extracellular matrix.

Front 38

Maturation

Back 38

As plaque accumulates and matures, a shift from a predominantly gram-positive flora to gram negative, anaerobic flora occurs.
Fusobacterium nucleatum, Porphyromonas gingivalis and Eubacterium Spp.
Complex nutritional, spatial and genetic relationships are present


Fluctuations in bacterial populations may arise in mature plaques.
Changes in available nutrients, enzymatic activities or host responses may trigger these fluctuations.

Front 39

Non specific plaque hypothesis

Back 39

Non-specific plaque hypothesis proposes that plaque causes dental diseases. Oral hygiene and other methods of preventing plaque accumulation will control these diseases.

Front 40

Specific plaque hypothesis

Back 40

pathogenic bacteria that colonize plaque initiate dental disease.
Preventive approaches can be extended to include immunization and other methods to eliminate specific pathogens.

Front 41

What did some association studies find about the distribution of Mutans Streptococci on tooth surfaces? Salivary levels?

Back 41

Fissure>proximal>buccal>lingual

Gnotobiotic technology showed that without bacteria, dental caries won't occur.

Salivary levels of MS strongly associated with caries experience.
Caries risk Assessment.

Based on this, they knows that MS is necessary but not sufficient.

Front 42

What did longitudinal studies reveal about the role of MS?

Back 42

-several studies looked at fissure, interproximal deay
-increases in MS usually preceded by caries initiation.

Front 43

What did response to treatment studies do about dental caries?

Back 43

Successful treatment should lead to changes in the bacterial flora.
Prospective studies can be performed to monitor levels of suspected pathogens before, during and after treatment.
Subsequent caries experience of subjects can also be monitored.

Front 44

MS characteristics
1. What does it ferment?
2. Shape?

Back 44

Characteristics of MS: ferment mannitol and sorbitol, synthesize extracellular glucans from sucrose, cariogenic in animal models.
More oval than round.
Original divided into serotypes (a,b,c,d,e,f,g,h) and four genetic groups
Now divided into distinct species.

Front 45

Name 5 virulence determinants of cariogenic bacteria

Back 45

Sugar transport
Acid production
Aciduricity
Extracellular polysaccharide production
Intracellular polysaccharide production

Front 46

Describe sugar transport

Back 46

High and low affinity transport systems operate over a wide range of environmental condtions to ensure substrate uptake even under extreme conditions (e.g. low pH)


Generally, expression of PEP-PTS is constitutive, High affinity system.
Most active at low substrate concentrations,repressed in high concentrations of sugar.
Also repressed in MS in low pH. (MS produced acid at low pH, must be other systems involved.)
Normal pH, low sugars.


Another system is called pmf (proton motive force system) Transports free carbohydrate, phosphorylation occurs intracellularly.
In MS, operates optimally at pH 5.5. Low pH, lots of sugar around.

Front 47

Acid production

Back 47

An efficient glycolytic pathway rapidly produces low terminal pH values in plaque.


After sugars are transported into cell, can be:
generate biomass via anabolic pathways.
Broken down to organic acids (e.g. glycolysis) to generate energy.
Acid production has been studies extensively due to role in demineralization of enamel.


Anaerobic fermentation
Convert pyruvate to lactate (via lactate dehydrogenase) when sugars are in excess.
Convert pyruvate to formate, acetate, and ethanol under carbohydrate limitation.

Front 48

What is the last step in acid production?

Back 48

Lactic acid production is fundamental to virulence.
MS lac dehydrogenase mutants (form no lactic acid) are able to infect host animals, for plaque and persist on tooth surface. Fail to decay teeth

Front 49

What lead to the development of the ecological plaque hypothesis?

Back 49

These three characteristics (efficient sugar transport, rapid acid production and aciduricity) have led Marsh (1994) to propose and Ecological Plaque Hypothesis.

Front 50

What do extracellular polysaccharides contribute to?

Back 50

EPS contribute to the plaque matrix, consolidates attachment of cells and may localize acidic fermentation products.
Consistent with the association of Sucrose with Dental Caries.
Synthesize long repeating polymers of glucose (Glucan)

Front 51

Describe the adhesion by MS with sucrose independent and sucrose dependent pathways?

Back 51

Sucrose Independent
-Mediated by Surface Molecules/Fibrils
-Initial Attachment/Reversible


Sucrose Dependent
-Mediated by Glucans
-Stabilized attachment
-enzymes invovled in EPS synthesis are highly specific for sucrose.

Front 52

How do MS store carbohydrates?

Back 52

MS store carbohydrate as intracellular polysaccharides.
Many strains of oral strep. can synthesize polymers resembling glycosgen (1,4-a-glucan)

Front 53

Describe 5 cariogenic features of mutans Streptococci

Back 53

Binding to and colonization of teeth
Accumulation on tooth surfaces.
Production of acid
Tolerance of high concentrations of sugar, low pH.

Association with Dental Caries in humans
Causation of Dental Caries in experimental animals
Transmissible in animals and apparently in man.

Front 54

What are some factors that might influence MS virulence/levels in the mouth?

Back 54

-fluoride: Inhibits sugar transport by blocking PEP-PTS system (Low availability of PEP)
- interferes with IPS synthesis and inhibits other enzymes that influence bact growth
-diet - high correlation in several studies between sugar and DMFS.
frequency of carbs is critical.
-immune response (natural)
hereditary fructose intolerance