Oral bacteria and Dental disease

Question 1

What environmental conditions (nutrient source, pH, and redox potential) are characteristic of the different sites that dental plaque is found?

Answer 1

Fissures: saliva and diet, neutral-acid, and positive
Approximate Surfaces: saliva, diet, and GCF (gingival crevicular fluid), neutral to acid, and slightly negative
Gingival Crevice: GCF, neutral to alkaline, and negative

organisms found on all surfaces of the oral cavity: streptococcus mitis

Question 2

What is biofilm?

Answer 2

a biofilm is a community of bacteria attached to a surface this is encased in an extracellular polymer substance or EPS. The biofilm formation aids the participating bacteria by:

1) providing protection against host defenses
2) limit the diffusion of nutrients
3) protection against antimicrobial substance
4) providing energy storage
5) quorum sensing

Question 3

What is quorum sensing?

Answer 3

a form of bacterial communication that allows a community of bacteria to coordinate gene expression in response to the size of the population or environmental cutes. This is achieved through the release of an “autoinducer” molecule that is released by all members of a particular species. Once enough of these molecules bind to “transcriptional regulators” on the cell surface, target gene expression will be induced.
Note: “enough molecules” is based on the threshold value of that particular transcriptional regulator.

Question 4

How can S.mutans contributes to disease - cause damage?

Answer 4

Smutans has a variety of virulence factors that contribute to dental caries:
1) acidogenic: ability to metabolize carbs and produce acid
2) acid tolerant: ATR (acid tolerant response) more tolerant to acidic environment than commensal bacteria
3) glycolsyltansferase (GTF): extracellular enzymes that forms polymers of glucose from sucrose, liberating fructose (think biofilm formation. Importantly, GTFs only work while in the presence of sucrose). Most strains of S. mutant have 3 GTFs.
-glucan binding proteins: (Gbp) surface proteins that bind glycan
Note: some of the s. mutant stereotypes contain Cnm collagen binding proteins, which are linked to cardiovascular disease and stroke

Question 5

How could health associated commensal organisms be used to treat dental caries?

Answer 5

commensal bacteria could be used to prevent dental caries by:

1) s. oligofermentans : production of H2O2 from lactic acid which will inhibit S. mutant metabolizes lactic acid
2) S. Australis - production of NH3 from arginine which will raise plaque pH
3) S. Gordonii: production of a protease that degreases CSP and ultimately antagonizes S. mutans

Question 6

What is periodontitis and what virulence factors of Pg contribute to the development of disease?

Answer 6

periodontitis is a chronic inflammatory diseases which affects the tooth-supporting tissues or periodontist, and also increases the risk for other inflammatory diseases (atherosclerosis, diabetes, and possible rheumatoid arthritis). Virulence factors include:

1) capsule: anti-phagocytic, down regulates cytokine production, encapsulated strains more virulent
2) Gingipains (proteases) - degrades extracellular gastric components, cytokines, immunoglobulin, and complement factors. Decreased fibrinogen which increases bleeding
3) Fimbriae: required for binding to host cells and invasion
4) LPS - lipid A modification evade or antagonize TLR4 interactions