Periodontal Microbiology

Question 1

Explain the experimental gingivitis model.

Answer 1

Human volunteers with clean teeth and clinically healthy gingival tissues abolished oral hygiene practices leading to plaque deposits covering almost all tooth surfaces and consequently developing a generalized marginal gingival inflammation.

Question 2

What are two early studies done in oral microbial research?

Answer 2

1. cultivation

2. microscopy

Question 3

The ___ ___ Anomaly is the difference between what is seen on microscopy versus what is grown on a plate (cultivation).

Answer 3

Great Plate

Question 4

A ___ is an organized cooperating community of organisms with specific inter-bacterial and host-bacterial interactions.

Answer 4

biofilm

Question 5

What occurs during the first and second stages of biofilm formation?

Answer 5

1. Free-swimming bacterial cells align on a surface, arrange themselves in clusters and attach.
2. the collected cells begin producing a gooey matrix

Question 6

Which stage are the following?
A. The cells signal one another to multiply and form a microcolony.
B. Some cells return to their free-living form and escape, perhaps to form new biofilms.
C. Chemical gradients arise and promote the coexistence of diverse species and metabolic states.

Answer 6

A - stage 3
B - stage 5
C - stage 4

Question 7

Planktonic bacteria adhere to the ___ ___, which is composed of salivary ___ and ___. This film alters the surface ___ and ___ energy, which in turn increases the efficiency of bacterial ___.

Answer 7

acquired pellicle; glycoproteins; antibodies; charge; free energy; adhesion

Question 8

T/F. Bacteria vary in their attachment ability.

Answer 8

True.

Question 9

___ attachers possess specific attachment structures (fimbriae, extracellular polymers, glycocalyx), which enable them to attach upon contact.

Answer 9

Rapid

Question 10

T/F. Slow attachers have specific mechanisms allowing them to attach.

Answer 10

False, slow attachers have NO specific mechanism

Question 11

How does bacterial characteristic change following attachment?

Answer 11

After attachment, bacteria change their phenotype.

1. synthesis of new outer membrane proteins
2. active cellular growth

Question 12

___ is cell-to-cell recognition of genetically distinct cell types mediated by protein or glycoprotein receptors on one cell and carbohydrates on the other.

Answer 12

Co-aggregation

Question 13

T/F. In co-aggregation, all cells are suspended and once a ‘clump’ forms attachment to pellicle occurs.

Answer 13

True.

Question 14

___ interactions between suspended and already adhering micro-organisms.

Answer 14

Co-adhesion

Question 15

Co-adhesion is influenced by temperature (no co-adhesion > ___ degree) and lactose ( increased lactose = ___ co-adhesion).

Answer 15

37; decreased

Question 16

During biofilm fomation maturation, there is an ___ in diversity, ___ and ___ formation, and ___ succession.

Answer 16

increase; replication; matrix; ecological

Question 17

Define ecological succession.

Answer 17

Increase in type and number of species.

Question 18

Primary colonizers are gram ___ (Strep) and ___ (Actino) that bind pellicle proteins from saliva. Secondary colonizers (gram ___) are bridge species (f. nucleatum) and bind other bacteria. Tertiary colonizers (gram ___) are not normally present in enough numbers to be pathogens.

Answer 18

positive; negative; negative; negative

Question 19

T/F. As the biofilm increases in thickness, there is no difficulty in diffusion in and out of the biofim as a sodium gradient develops.

Answer 19

False, As the biofilm increases in thickness, there IS difficulty in diffusion in and out of the biofilm and an OXYGEN gradient develops.

Question 20

Completely anaerobic ( NO ___) conditions emerge in the deeper layers and a reverse gradient of ___ products develop as a result of bacterial metabolism.

Answer 20

oxygen; fermentation

Question 21

How does a supragingival plaque get nutrition? Subgingival?

Answer 21

SUPRA - dietary products dissolved in saliva

SUB - periodontal tissues and blood

Question 22

What is used to breakdown host macromolecules into peptides and amino acids?

Answer 22

bacterial hydrolytic enzymes

Question 23

The biofim is made up on ___ (15-20% volume) + interbacterial ___.

Answer 23

microcolonies; matrix

Question 24

What are the three sources of matrix?

Answer 24

1. dead bacterial cells
2. saliva
3. gingival exudate

Question 25

T/F. There is a presence of voids or water channels in the bioflim.

Answer 25

True.

Question 26

What makes up the backbone of the biofilm?

Answer 26

exopolysaccharides

Question 27

The lower layer of the biofilm includes a dense layer of ___ with a ___ matrix that is tightly bound together with steep ___ gradients.

Answer 27

microbes; polysaccharide; diffusion

Question 28

The ___ layer of the biofilm is irregular in appearnce and extends into the surrounding medium.

Answer 28

loose

Question 29

The ___ layer of the biofilm is a stationary sublayer with fluid in motion that nourishes the biofilm by ___ diffusion.

Answer 29

fluid; molecular

Question 30

What determines the shape of micro-colonies?

Answer 30

It depends on shear force due to the passage of fluid over the biofilm

Question 31

T/F. If the shape of a micro-colony is in the form of a tower or mushroom, then it is under high shear force. Whereas, elongated colonies capable of oscillation are under a low shear force

Answer 31

False, at low shear force, colonies are shaped like towers or mushrooms, while at high shear force, the colonies are elongated and capable of rapid oscillation.

Question 32

The interbacterial matrix is highly variable. Gram positive matrix is very ___ due to dextrans and levans.

Answer 32

fibrillar

Question 33

Gram negative matrix is very regular because it contains ___ vesicles filled with ___ and proteolytic enzymes that are probably involved in ___.

Answer 33

tri-laminar; endotoxins; adherence

Question 34

Interbacterial carbohydrates have an energy source from ___ and ___. The skeleton of plaque is ___.

Answer 34

dextrans; fructans; mutans

Question 35

What forms between the subgingival plaque and the tooth?

Answer 35

Cuticle, an electron dense organic material. This structure is similar to supragingival plaque

Question 36

T/F. It is unsure whether the cuticle originated from an epithelial attachment, crevicular fluid, or was secreted by adjacent epithelium. BUT its location in the subgingival area makes it unlikely that salivary constituents contributed to its formation.

Answer 36

True.

Question 37

Is the bacterial layers near the sulcular epithelium different from tooth-attached?

Answer 37

Yes, there is no definite inter-microbial matrix and more spirochetes and flagellated bacteria that are capable of motility are present.

Question 38

Streptococcus ___ is a ___ species that can live with or without O2. It uses up O@ when available.

Answer 38

cristatus; facultative

Question 39

Fusobacterium ___ is a robust ___ that binds to Strep and improves survival when O2 is present.

Answer 39

nucleatum; anaerobe

Question 40

___ gingivalis is a ___, ___ anaerobe whose coaggregation is essential to survival when O2 is present.

Answer 40

Porphyromonas; microaerophili, obligate

Question 41

F. ___ invades epithelial cells for protection but S. ___ does not invade cells. What happens after co-aggregation?

Answer 41

nucleatum; cristatus

S. cristatus is carried inside by F. nucleatum

Question 42

Defense is an advantage to living in a biofilm. There is a presence of concentrated bacterial ___ and a ___ matrix.

Answer 42

enzymes; interbacterial

Question 43

When living in a biofilm, bacteria are protected from external changes because ___ is minimal in interior regions, antibiotic and antimicrobial resistance, protection from ___ and ___ forces, and ___.

Answer 43

diffusion; friction; shearing; attachment

Question 44

How can bacteria transfer info and genetic material while living in a biofilm?

Answer 44

signaling (quorum sensing)
conjugation
transformation
plasmid transfer
transposon transfer

Question 45

___ ___ is the regulation and expression of specific genes through accumulation of signaling compounds that mediate intercellular communication.

Answer 45

Quorum sensing

Question 46

What does quorum sensing depend upon?

Answer 46

cell density

Question 47

How does quorum sensing work?

Answer 47

Auto-induction 1 or 2 leads to increased concentration as cell density increases. Once signaling compounds reach a threshold level, gene expression is activated.

Question 48

T/F. Expression of genes for antibiotic resistance at high cell densities may provide protection.

Answer 48

True.

Question 49

T/F. Quorum sensing does not have the potential to influence community structure by encouraging the growth or beneficial species and discouraging the growth of competitors.

Answer 49

False, Quorum sensing DOES have the potential to influence community structure by encouraging the growth or beneficial species and discouraging the growth of competitors.

Question 50

T/F. Commensal species produce and respond to high levels of autoinducer - 2, while pathogens produce and respond to low levels of these substances.

Answer 50

False, Commensal species produce and respond to LOW levels of autoinducer - 2, while pathogens produce and respond to HIGH levels of these substances.

Therefore, AI-2 may determine the switch between commensal to pathogenic communities.

Question 51

Biofilm bacteria are ___-___ times more resistant than planktonic bacteria to antibiotics.

Answer 51

1000-1500

Question 52

Why is it a good mechanism of antibiotic resistance that biofilm bacteria grow more slowly?

Answer 52

1. Antibiotics depend on cell turnover for efficacy
2. Slow-growers express ‘non-specific defense mechanisms’
3. Slow growers make more exo-polymers

Question 53

How do exo-polymers retard diffusion?

Answer 53

1. Ion-exchange mechanism prevents highly charged molecules from reaching deeper zones
2. Extracellular enzymes (beta-lactamases, formaldehyde dehydrogenase, formaldehyde lyase) inactivate antibiotics

Question 54

Biofilm bacteria are able to evade antibiotics because they express different genes due to gene ___ and ___ expression of biofilm existence.

Answer 54

transfer; phyenotypic

Question 55

T/F. Classically, a pathogen is not normally present and produces virulence factors that damage the host directly (toxins) or induce host to damage itself (immune responses).

Answer 55

True.

Question 56

Why is it that presumed oral pathogens don’t quite fit the model of a classical pathogen?

Answer 56

1. normally present throughout life

2. damage requires presence in large numbers

Question 57

Explain the ecological concept of oral microbial diseases.

Answer 57

1. Ecological shifts lead to changes in proportions
2. Balance shifts in favor of “pathogens”/disease
3. Periodontal disease is an example of ‘ecological catastrophe’

Question 58

Why is the structure of biofilms clinically significant?

Answer 58

Changed tooth-brushing paradigms
Hard to reach interproximal and fissures
Non-contact brushing can remove towers and mushrooms by shear forces

Question 59

Antibiotic sensitivity testing distinguishes between ___ and ___ bacteria.

Answer 59

planktonic; biofilm

Question 60

What are some targets for biofilm therapy?

Answer 60

AI-2

vaccines that target common resistance genes

Question 61

The periodontal ___ can translocate pathogens from pockets to health sites.

Answer 61

probe

Question 62

T/F. Drug-resistant strains can translocate to neighboring teeth, teeth can act as reservoirs for colonization of implants., and bacteria can infect membranes in GTR.

Answer 62

True.

Question 63

What is the rationale for one-stage, full-mouth disinfection by Leuven?

Answer 63

Full-mouth scaling and root-planing within 24 hrs.
Subgingival irrigation with 1% chlorhexedine
Tongue brushing
Oral antimicrobial rinse

Question 64

Plaque can form on ___ abutments. Those that fail have a microbial composition similar to ___ disease.

Answer 64

implant; periodontal