Past paper questions

Question 1

What term can be used to describe collective group of microorganisms within oral cavity and what are they referred to when attached to surface?

Answer 1

• Microbiome Biofilm

Question 2

List four key microbial stages of caries plaque formation?

Answer 2

• Adhesion
• Colonisation
• Maturation
• Dispersal

Question 3

Name two key virulence factors used by Streptococcus mutans to influence enamel dissolution?

Answer 3

• ATPase to control pH environment
• Glucans to attach to tooth

Question 4

Name the bacterium associated with secondary endodontic infections

Answer 4

• E.faecalis

Question 5

Name one of E.faecalis key virulence factors?

Answer 5

• Endotoxins - LPS
• Adhesins

Question 6

Why is it difficult to determine causality from a specific bacteria endodontic infcetion?

Answer 6

• Can’t ensure no contamination
• Difficult to obtains a sterile sample

Question 7

Which antimicrobial is primarily used to disinfect root canal?

Answer 7

• Sodium hypochlorite

Question 8

What culture independent technique could be used to assess changes in oral microbial populations following antibiotic exposure?

Answer 8

• Next generation sequencing

Question 9

What is the limitations to next generation sequencing?

Answer 9

• Limited to describing what is present rather than activity of the community

Question 10

4 factors that cause candidosis

Question 11

Name the organism and virulence factor which causes candidosis?

Question 12

What aids adhesion and acid tolerance in caries forming microorganisms?

Question 13

How can S.mutans survive high acidic environments and stick to each other? ie virulence factors

Answer 13

-Adhesins - SpaP: makes up fibrillar layer of cell wall
-Binding Proteins - glucosyltransferase, fructosyltransferase, glucan binding protein
-Sugar Modifying Enzymes: fructanase, dextranase Polysaccharides
-Acid Tolerance & Adaptation:F1F0 ATPase

Question 14

Virulence factors involved in periodontal disease?

Answer 14

• Porphyromonas gingivalis:
  — Host cell adherence and invasion – fimbriae
  — Elaboration with proteases – collagenase, fibrinolysinl phospholipase A and ohosphotases — Endotoxins (LPS)
  — Capsular polysaccharide and outer membrane vesicles
  — Tissue toxic metabolic by products – hydrogen sulphide, ammonia and fatty acids

Question 15

Why do biofilms not allow antibiotics to penetrate them?

Answer 15

• Biofilms can produce a penetration barrier of LPS which prevents antimicrobials and antibiotics from penetrating.
• Biofilms also require mechanical disruption so alone medications will not work to remove them fully.
  -The biofilm Impairs diffusion
  -It causes binding of Antibiotics
• Extracellular DNA Persisters