Microbiology - GT

Question 1

What is the difference between resident and transient microbes?

Answer 1

L12

resident: always present
transient: present under certain conditions e.g. time

Question 2

What are the benefits of indigenous microbes?

Answer 2

L12

• aids digestion/nutrition
• antagonism/competition with pathogens = colonisation resistance
• constant stimulation of the immune system
• tissue development (angiogenesis)

Question 3

What are the conditions that promote opportunist pathogens?

Answer 3

L12

• immunocompromisation
• introduction to microbes to unusual sites
• disturbances to normal microbiota (antibiotics)

Question 4

What are the gram + and gram - bacteria that dominate the skin?

Answer 4

L12
Gram +ve
- staphylococcus
- micrococcus
Gram -ve
- corynebacterium
- propionibacterium

Question 5

How does bacterial colonisation to the tooth surface occur?

Answer 5

L14

• adherence to specific receptors in the acquired enamel pellicle
• binding mediated by microbial surface proteins called adhesins

Question 6

What is the acquired enamel pellicle?

Answer 6

L14

• a protein film that forms on the surface enamel
• derived from saliva due to selective adsorption of certain molecules

Question 7

What is the definition of dental plaque?

Answer 7

L14
the complex microbial community found on the tooth surface embedded in a matrix of polymers of bacterial and salivary origin

Question 8

What are the stages involved in plaque development?

Answer 8

L14

• clean enamel surface
• pellicle formation (2 sec)
• pioneer bacteria (2 min)
• microcolonies and extracellular polysaccharide (2 hours)
• biofilm development (2 hours +)
• mature plaque + sealing in bacteria (48 hours)

Question 9

What is an example of pioneer bacteria in dental plaque formation?

Answer 9

L14

- streptococcus sanguis

Question 10

How is difference between supragingival and subgingival plaque?

Answer 10

L14
supragingival:
- >90% gram +ve
- cocci and filaments
- carbohydrate fermentation = acidogenic
- microaerophilic (low oxygen levels)
- bathed by saliva
- dental caries
subgingival:
- >50% gram -ve
- rods and fusiforms 
- saccharolytic and asaccharolytic (proteolytic)
- anaerobic 
- bathed by gingival cervicular fluid
- periodontal disease