3 - Biofilm 2: Periodontal disease

Question 1

What influences oral microflora?

Answer 1

• host factors (systemic disease, antibiotics, hygiene)
• diet (composition, frequency)
• saliva (flow rate, pH, antimicrobial factors)
• GCF (antimicrobial)
• microbial interactions (competition, symbiosis)
• gaseous environment

Question 2

What do bacteria release that increase the rate of progression towards periodontal disease?

Answer 2

• cytotoxins
• proteinases
• LPS

Question 3

Describe the development of the biofilm related to periodontal disease.

Answer 3

• naked surface
• conditioning film (host salivary glycoproteins)
• linking film (streptococcus)
• co-aggregation and re-conditioning film (actinomyces)
• accumulation and shedding, eg the spread of disease (fusobacterium)

Question 4

What are the key microorganisms present in a healthy periodontium?

Answer 4

• oral streptococci (gram positive)
• actinomyces
• veillonella
• haemophilus
• neisseri
• fusobacterium

Question 5

What are the key microorganisms present in a gingivitis?

Answer 5

• actinomyces
• prevotella intermedia
• bacteroides
• fusobacterium nucleatum

Question 6

What are the key microorganisms present in a diseased periodontium?

Answer 6

• prophyromonas gingivalis *
• tannerella forsythia*
• treponema denticola *
• prevotella intermedia
• A. a

Question 7

Describe microbial competition.

Answer 7

• dominance of a biofilm
• metabolic products can toxic to other species (acids or oxidants)
• bacteriocins
• receptor antagonism

Question 8

Describe microbial cooperation.

Answer 8

• integration and symbiosis of bacteria in the biofilm
• metabolic products that support other bacteria (saccharides, peptides, growth factors)
• adhesion substrates allow biofilm to form
• immune avoidance

Question 9

What is a commensal community?

Answer 9

A biofilm present in a healthy mouth that avoids disease by constraining pathogens or excluding them (ie preventing adhesion)

Question 10

What properties make P. ging a keystone pathogen for periodontitis?

Answer 10

• host cell tissue adhesion via fimbriae
• multiple proteases (collagenase, fibrinolysin, phospholipase A, phosphatases)
• endotoxin (LPS)
• capsular polysaccharide that has outer membrane vesicles
• by-products that are toxic to tissues (hydrogen sulphide, ammonia, fatty acids)

Question 11

Describe the adhesion of P. ging.

Answer 11

• fibrillar adhesions help to invade membranes of host cells
• long fimbriae are the initial attachment
• short fimbriae which allows cell to cell aggregation and allows formation of microcolonies

Question 12

What is gingipains?

Answer 12

• protease
• manipulates the biofilm and host defences
• causes degradation of innate receptors and cytokines
• causes tissue destruction via MMPs
• uses subversion by tricking the host system

Question 13

What are the properties of A. a that make it a key stone pathogen?

Answer 13

• produces leukotoxin, cytotoxin and LPS
• has membrane vesicles
• has fimbriae for attachment
• can subvert host immune system
• has a glycoprotein matrix