Periodontal Microbiology #4 Flashcards
Roughy how long does it take (without brushing) for the average person to get gingivitis?
14 days
There are more than ______ species of bacteria found in the mouth.
700 (most individuals has about 60)
What is a plaque biofilm?
Organized cooperating community of organisms with specific inter-bacterial and host-bacterial interactions. (not just one type of bacteria)
Is gingivitis only bacteria induced?
NO! viruses and fungi have been implicated too
You remove ____% of plaque when you brush?
40
What are the stages of plaque formation?
Pelllicle formation? Attachement Growth Maturation Ecological succession
What is the difference between rapid and slow attachers?
- Rapid have specialized methods of attachment structures (fimbriae)
- Slow attachers have no specific mechanism for attachment.
When does co-aggregation and co-adhesion occur?
During the growth stage!
_____ is cell-to-cell recognition of genetically distinct/different cell types.
Co-aggregation ** This is mediated by protein or glycoprotein receptors on one cell and carbohydrates on the other.
_____ is the interactions between suspended and already adhering micro-organisms.
Co-adhesion
What factors influence Co-adhesion?
Increase in Lactose = decrease in co-adhesion
Temperature = no co-adhesion greater than 37 degrees
What is the purpose of Co-aggregation?
To form clumps of bacteria that can attach to the pellicle.
* This is mediated by protein or glycoprotein receptors on one cell and carbohydrates on the other.
Describe what happens during the Maturation stage of biofilm formation.
- Increase in diversity
- Replication and matrix formation
- Ecological succession
What types of bacteria are Primary or Early colonizers?
Gram + and Gram -
Streptococci bind pellicle proteins from saliva
*Primary colonizers are associated with health!
What Types of bacteria are Secondary colonizers?
Gram Negative bridge species (F. Nucleatum Prolific coaggregator) bind to other bacteria
What types of bacteria are Tertiary colonizers?
Gram negative bacteria (prophromonas gingivalis)
What occurs environmentally when the biofilm increases in thickness?
- Difficulty in diffusion join and out of the biofilm
- An oxygen gradient develops
- Completely anaerobic (no oxygen) conditions emerge in the deeper layers which can lead to fermentation.
- Reverse gradients of fermentation products develop as a result of bacterial metabolism.
What is the nutritional source for supra gingival plaque?
Dietary products dissolved in saliva
What is the nutritional source for sub gingival plaque?
Blood and Periodontal tissues
The structure of the biofilm can be described as ________ + _________.
Micro-colonies (15-20% volume) + inter-bacterial matrix
What makes up the inter-bacterial matrix of the biofilm?
- Dead bacterial cells
- Saliva
- Gingival exudate
_______ are considered the backbone of the biofilm.
Exopolysaccharides
What are the 3 layers of a biofilm?
- Lower layer = dense layer of microbes w/ steep concentration gradient.
- Loose layer
- Fluid layer = nourishes the biofilm by molecular diffusion
How does the physical structure of plaque differ?
Shape of colonies depend on shear force exposure.
- Interproximal (Supra gingival) = towers or mushrooms due to low shear force.
- Buccal side of teeth (supra) = elongated colonies capable of oscillation and withstanding high shear force.
- Subgingival plaque is similar to supragingival plaque in structure.
Describe the Structure of the inter-bacterial matrix of plaque…
It is highly variable…
- Gram + matrix is very fibrillar due to dextran and levans.
- Gram Negative matrix is very regular (Increases in health!), contains trilaminar vesicles filled with endotoxins and proteolytic enzymes.
- Inter-bacterial carbohydrates = energy source for dextran and fructans. *also skeleton of plaque
What is the main differences in structure between supra gingival plaque and subgingival plaque?
Sub gingival = cuticle forms primary attachment
*Bacterial layers near surface epithelium are different from tooth attached plaque (No inter-bacterial matrix and have more spirochetes and flagellated bacteria)
Supra gingival = plaque is attached by salivary pellicle.
Which level of colonizers illicit the most immune response?
Tertiary colonizers
Bacterial collaboration is necessary for ________.
Succession
What kind of environment does Streptococcus Cristatus need?
- Facultative species (can live with or without O2)
- Uses up O2 when available
What kind of environment does Fusobacterium nucleatum need?
- Robust ANEROBE
- Binding to Strep improves survival when O2 is present (Example of Bacterial collaboration)
What kind of environment does Porphyromonas gingivalis need?
- Microareophilic, obligate anaerobe
- Coaggregation essential to survival when O2 is present
Strep, Fuso and Porphyro form a robust biofilm in the presence of O2.
Good to know
What are the 3 main advantages for bacteria as part of a biofilm?
- Defense = concentrated bacterial enzymes
- Protection = from friction, antibiotics, and diffusion is limited in interior regions.
- Transfer of info and genetic material = signaling, conjugation…..
What is Quorum sensing?
Regulation of expression of specific genes through accumulation of signaling compounds that mediate intercellular communications.
What are the benefits of Quorum sensing?
- Antibiotic resistance in dense biofilms
- encourages growth of beneficial species
Commensal bacterial produce and respond to _____ levels of Al-2.
Low
_______ produces Al-2 in high levels.
Pathogens
______ may determine the switch from commensal to pathogenic community.
Al-2 presence
Antibiotics depend on _____ for efficacy.
Cell turnover *Important b/c antibiotic resistant bacteria usually have slow turnover rates.
Biofilm bacteria are ______ time more resistant than the planktonic variety.
1000-1500 times more resistant
What do Exo-polymers do in regards to antibiotic resistance?
They retard diffusion of antibiotic *slow growing bacteria make Exo-polymers.
What is the significance of the fact that biofilms express different genes?
It increases antibiotic resistance
What is the Classic concept of a pathogen?
- Not normally present
- Produce virulence factors (damage to host)
Do oral pathogens fit the classic concept?
No, b/c they are normally present through out life and damage usually requires large numbers
_______ leads to changes in “pathogen” proportions
Ecological shifts
Can perio probing translocate bacteria?
Absolutely
