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AU 15 - Periodontology > Periodontal Microbiology > Flashcards

Periodontal Microbiology Flashcards

1
Q

What was the mode of early microbiology experiments?

What’s the issue with this?

A

Growing things on a plate

The problem is the “we know what we can grow” bias

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2
Q

What revolutionized microbiological study?

A

Molecular appraoaches

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3
Q

How many distinct oral species can be in a person?

A

40-60

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4
Q

Core microbiome

A

About 8% of species seen in a person’s mouth are seen in other people’s mouth
These microbiomes can change with ethnicities

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5
Q

The plaque biofilm definition

A

Organized cooperating community of organisms with specific inter-bacterial and host-bacterial interactions

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6
Q

T/F - you expect to see all 5 stages of biofilm formation in the mouth

A

False - we can brush and tongue away biofilm

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7
Q

What are the main species of Primary colonizers

A

Strep sanguis

Actinomyces viscosus

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8
Q

What occurs during the Attachment phase of biofilm formation?

A

Planktonic bacteria adhere to an acquired pelicle

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9
Q

What is in a pellicle t make bacteria attach to it?

A

Glycoproteins and antibodies

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10
Q

What bacterial characteristics change following attachment?

A

Synthesis of outer membrane proteins (this is what our body sees as foreign bodies)
Active cellular growth

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11
Q

What occurs during the growth stage of biofilm formation?

A

Co-aggregation and Co-adhesion

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12
Q

Co-aggregation

A

Cell-to-cell recognition of genetically distinct cell types

Cell clumps form and attach to a pellicle

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13
Q

Co-adhesion

A

Interactions between suspended and already adhering micro-organisms

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14
Q

What influences co-adhesion?

A

Temperature (no coadhesions below 37 C)

Lactose (more lactose means less co-adhesion)

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15
Q

Most of what we do to prevent caries effects what?

A

Co-adhesion

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16
Q

What occurs during biofilm maturation?

A

Increase in diversity
Replication and matrix formation
Ecological succession

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17
Q

Primary colonizers

A

Gram+ and Gram- streptococci that bind to pellicle proteins form saliva

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18
Q

Secondary colonizers

A

Gram- species that bind to the bridge species

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19
Q

Why do secondary colonizers need to bind to a bridge species?

A

They can’t bind to the tooth, so they have to bind to bacteria

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20
Q

What is known as the “bridge species”?

A

F. nucleatum

21
Q

Tertiary colonizers

A

Gram- species that bind

Our body sees these as pathogens

22
Q

How does the biofilm environment change when it increases in thickness?

A

Difficulty diffusing things in and out of the biofilm
An oxygen gradient develops
Completely anaerobic conditions emerge in the deeper layers (streps start to die, which allows pathogenic species to come in)
Reverse gradients of fermentation products develop as a result of bacterial metabolism

23
Q

What provides nutrients to the supragingival plaque?

A

Dietary products dissolved in teh saliva

24
Q

What provides nutrients to the subgingival plaque?

A

Periodontal tissues and blood

bacterial hydrolytic enzumes breakdown host macromolecules into peptides and amino acids

25
Q

Describe the structure of a biofilm

A

Microcolonies (15-20% of volume)
Interbacterial matrix
Voids/water channels
Exopolysaccharides provide the backbone of the biofilm
There is a lower layer, loose layer, and a fluid layer

26
Q

Describe the lower layer of a biofilm

A

Dense layer of microbs
Polysaccharide matrix
Tightly bound together
Steep diffusion gradient (things can’t get down there)

27
Q

What’s the best way to remove the lower layer of a biofilm?

A

Mechanical therapy

28
Q

Describe the loose layer of a biofilm

A

Irregular in appearance

Extends into surrounding medium

29
Q

Describe the fluid layer of a biofilm

A

Stationary sublayer
Fluid layer is in motion
Nourishes the biofilm by molecular difusion

30
Q

Describe the structure of supragingival plaque

A

The shape depends on shear force

The interbacterial matrix is highly variable

31
Q

What is the shape of supragingival plaque under low shear force?

A

Towers or muschrooms

32
Q

What is the shape of supragingival plaque under high shear force?

A

Elongated colonies capable of oscillation

33
Q

What is the consistency of a gram+ matrix of supragingival plaque going to be?

A

Very fibrilar

34
Q

What is the consistency of a gram- matrix of supragingival plaque going to be?

A

Very regular

35
Q

What are the advantages to biofilm living?

A

Defense
Protection from external changes
Transfer of info and genetic mateiral

36
Q

What is quorum sensing?

A

Regulation of expression of specific genes through accumulation of signaling compounds that mediate intercellular communication
Bacteria in biofilms are constantly talking and interacting to see if there’s enough of them to do damage

37
Q

Why are biofilms more resistant to antibiotics than planktonic bacteria?

A

Antibiotics depend on cell turnover
Biofilm cells grow slower, so they are not going through DNA replication as often
Slow growing bacteria express ‘non-specific defense mechanisms’ and more exopolymers

38
Q

Exopolymers

A

Retard diffusion with an ion exchange mechanism that prevents charged ions from reaching deeper zones
They also have extracellular enzymes that breakdown antibiotics

39
Q

What is the classic model of a true pathogen?

A

Microorganism that isn’t normally present and produces virulence factors that damage the host or produces an immune response

40
Q

Are there true oral pathogens?

A

No
Oral ‘pathogens’ are normally present throughout life
Damage from oral pathogens require presence in large numbers - ecological shifts lead to changes in proportions/balance which favors pathogens/disease

41
Q

Auto-inducer 2

A

AI-2 may determine the switch from commensal to pathogenic community
Can turn on in response to cell density in a biofilm
Commensal bacteria produce and respond to low levels of AI-2
Pathogens produce at high levels of AI-2

42
Q

What is the clinical significance of the structure of a biofilm?

A

It changed tooth-brushing paradigm

Non-contact brushing (sonic waves) can remove towers and mushrooms by shear force

43
Q

What is the clinical significance in the antibiotic resistance of biofilms?

A

It changed antibiotic sensitivity testing

44
Q

What is a major target for therapy in biofilms?

A

Auto-inducer 2

45
Q

What is the top reason for implant failure?

A

Active periodontal disease - teeth act as reservoirs for colonization of implants

46
Q

How can drug-resistant pathogens translocate to neighboring teeth?

A

Periodontal probing

47
Q

What will decrease bacterial load more - full mouth scaling, or one quad at a time?

A

Full mouth scaling and root-planing within 24 hours has been shown to decrease bacterial load better

48
Q

What gets more care, a live tooth or an implant?

A

They get the same amount of care (but err on the side of the implant)

AU 15 - Periodontology (8 decks)

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