Microbiology

Question 1

forms of oral candidosis

Answer 1

pseudomembraneous
= thrush

erythematous
- atrophic, denture

hyperplastic
= leukoplakia

angular cheilitis

Question 2

what is the mode of action of azoles

Answer 2

inhibits fungal enzymes
inhibits ergosterol synthesis which is a vital component of fungal cells

makes less effective at regulating ion/molecule transport, disrupts essential cellular processes, compromised cell viability

Question 2

class of antifungals commonly used to treat pt with recurrent oral candidosis

Answer 2

azoles

Question 3

resistance mechanisms of candida that render it resistant to azoles

Answer 3

alters target site, reducing binding affinity of azoles to the enzymes and makes it resistance

efflux pump regulations to pump the drug outwith the cell meaning it cannot work and reduce concentration

biosynthesis pathway alterations
upregulation of stress responses

Question 4

name one species resistant to azoles

Answer 4

candida glabrata

Question 5

how to differentiate candida albicans and glabrata

Answer 5

albicans can form hyphae, glabrata cannot

Question 6

characteristics of biofilm extracellular matrix that confers resistance from antimicrobial agents

Answer 6

physical barrier
slowed diffusion
chemical sequestration
altered environment [pH]
gene transfer
efflux pumps

Question 7

name important bacteria clearly implicated in periodontal disease, based on Socranksys red disease complex

Answer 7

p.gingivalis
t.forsythia
t.denticola

Question 8

name bacteria associated with caries development

Answer 8

s.mutans
actinomyces
lactobacilus

Question 9

what key features enable carcinogenic organisms to stick to enamel surfaces and autoggregate and to survive within an acidic envrionment

Answer 9

adhesion
production of EPS which allow sticking
biofilm formation
glucan production
acid tolerance and production

Question 10

name systemic diseases that are associated with periodontal biofilms

Answer 10

CVD
diabetes
cystic fibrosis
rheumatoid arthritis
alzheimers
pancreatic cancer

Question 11

what term can be used to describe the collective group of microorganisms within the oral cavity
AND
what are they referred to when they are attached to a surface

Answer 11

oral microbiome

oral biofilms

Question 12

list the key microbial stages of caries plaque formation

Answer 12

formation of pellicle which is a thin protein film which covers tooth surface in contact with saliva

early colonisation where s.mutan etc adhere to this layer and metabolise dietary sugars into acids, leading to enamel demineralisation and initiation of carious lesions

biofilm maturation where bacterial populations grow and form biofilm structure known as plaque

environment becomes increasingly acidic, dissolution of hydroxyapatite, demineralisation and progression of plaque formation

Question 13

name bacterium associated with secondary endodontic infections

Answer 13

p.endodontalis

Question 13

virulence factors used by s.mutans to influence enamel dissolution

Answer 13

acid production
extracellular polysaccharide production [adhesion]
acid tolerance

Question 14

what is the key virulence factor of p.endodontalis

Answer 14

production of endotoxins - induces inflammation, triggers immune response, contributes to periapical tissue destruction
[LPS]

proteolytic enzymes - tissue destruction, affects host defense

Question 15

why is it difficult to determine causality from a specific bacteria in endodontic infections

Answer 15

polymicrobial nature

biofilm formation
sampling tissue
host response variability

Question 16

what culture independent technique cold be used to assess changes in oral microbial populations following antibiotic exposure

Answer 16

16s rRNA gene sequencing

Question 17

limitations of 16S rRNA gene sequencing

Answer 17

cannot reliably differentiate between closely related species or strains

PCR bias

Question 18

what antimicrobial is primarily used to disinfect the root canal

Answer 18

NAOCl
sodium hypochlorite

Question 19

factors which cause candidosis

Answer 19

immunocompromised, immunosuppressive drugs, advanced HIV, intra-abdominal surgery, central venous catheter, broad spectrum antibiotics, diabetes, trauma pt, burn unit, long term corticosteroid use

Question 20

name the organism and virulence factor which causes candidosis

Answer 20

candida albicans

hyphae, adhesions, hydrolytic enzymes
biofilm formation
antifungal resistance

Question 21

key stages in biofilm formation

Answer 21

adhesion
colonisation
maturation
complex community
dispersal
EPS production

Question 22

how would you test for candida albicans and suggest a lab identification method

Answer 22

take a swab and culture on Sobourads agar
if present - white, creamy, yeast colonies

germ tube formation

Question 23

examples of antifungals and mechanism of action for both

Answer 23

azoles -
fluconazole, indirectly target ergosterol in fungi cell wall by interrupting activity of enzyme that produces it
fungistatic

polyenes -
nystatin, directly target ergosterol and cause perforation and leakage of IC contents, fungicidal
higher virulence but less well tolerated

echinocandins -
micafungin

Question 24

is candida albicans or glabrata resistant to fluconazole

Answer 24

glabrata