Microbiology

Question 1

Caries

1. 2 key organisms
2. Virulence factors of one key organism
3. 3 methods of acid tolerance
4. 3 anti-caries activities of fluoride
5. 3 methods of preventing caries

Answer 1

1. S. mutans, lactobacillus acidophilus
2. Adhesins, binding proteins (glucosyltransferase), sugar-modifying enzymes, polysaccharides (glucans), acid tolerance and adaptation (ATPase)
3. Maintain pH balance (ATPase), alters cell membranes, protection and repair mechanisms
4. Systemic - incorporated into developing enamel as fluorapatite (remineralisation)
   Topical - incorporated into developing enamel as fluorapatite (remineralisation)
   Antimicrobial - inhibits plaque metabolism and ATPase action
5. Reduce CHO in saliva (diet), use fluoride, reduce tooth susceptibility to caries (fissure sealants)

Question 2

Perio

1. 3 key/red Socransky’s organisms
2. 3 virulence factors of one key organism
3. 3 systemic diseases linked with perio pathogens

Answer 2

1. P. gingivalis, T. denticola, T. forsythia
2. Gingipains (degrades chemokines, activates MMPs), adhesins, tissue-toxic metabolic by-products
3. Cardiovascular disease, rheumatoid arthritis, diabetes mellitus

Question 3

Candida

1. 3 types of oral candidosis/candidiasis
2. 2 causes of candidiasis
3. 2 candida species and how to differentiate
4. 3 virulence factors of one candida species
5. 2 types of anti fungal treatment and how they work
6. 3 methods of candida resistance
7. 4 key features of biofilm development

Answer 3

1. Pseudomembranous, erythematous, hyperplastic
2. Poor denture hygiene, catheter, surgery, immunocompromised
3. C. albicans and C. glabrata - C. glabrata is resistant to azole antifungals
4. Hyphae (formed by C. albicans when stressed), adhesins, hydrolytic enzymes (haeolysin, proteinase, phospholipase)
5. Azoles - fluconazole - fungistatic. Indirectly target ergosterol in fungi cell walls by inhibiting/interrupting the activity of the enzyme involved in its production (14a demethylase)
   Polyenes - nystatin - fungicidal. Directly target the ergosterol in fungi cell walls, causing perforation and leakage of intracellular contents
6. Antimicrobials can’t penetrate beyond surface layer of biofilm (without mechanical disruption of biofilm), degraded by enzymes, not active against non-target organisms, expression of biofilm-specific resistant genes
7. Adhesion, colonisation, accumulation to form a complex community, dispersal