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Microbiology for dentists > Extra Qs > Flashcards

Extra Qs Flashcards

1
Q

Are molecular identification methods based on the organism’s genotype or phenotype. And what about biochemical tests

A
  • Molecular identification = genotype

- Biochemical = phenotype

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2
Q

What does a PCR test do. And the 3 main steps

A
  • Amplifying specific regions of DNA

- Denaturing, annealing, elongation

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3
Q

What does Lancefield group system do

A

Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls

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4
Q

Name some bacteria that can be cultured on blood agar

A

strep pyogenes, hameophylius influenza, Neisseria species

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5
Q

What agar can bacteria that ferment lactose be selected for

A

MacConkey agar

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6
Q

What agar can salmonella be cultured on

A

XLD agar

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7
Q

What agar is used for urine samples

A

CLED agar

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8
Q

Out of staph and strep, which lacks catalase activity

A

streptococci

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9
Q

What indicator is used in urease test. If positive, what is the colour change

A
  • from yellow to pink

- phenol red is used

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10
Q

what indicator is used in a DNAase test. What is the colour change

A
  • Toluidine blue

- turns pinkish in the presence of free nucleotides or oligonucleotides that are released by degradation of the DNA

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11
Q

5 main steps in a gram stain

A
  1. Heat fix bacteria to slide
  2. Flood with crystal violet
  3. Rinse and flood with iodine
  4. Decolourise with acetone
  5. Safranin counterstain
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12
Q

In acidic conditions, hydroxyapatite dissolves because ions are removed from solution. Which ions are likely to be removed?

A

OH- and (PO4)3-

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13
Q

Relationship of IP and Ksp at critical pH

A

They are equal

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14
Q

What type of microorganism does Sabouraud dextrose select for and why

A

Fungal

Low pH of media suppresses bacterial growth

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15
Q

What is the antibacterial mechanism of action of chlorhexidine?

A

Disrupts cell walls

Chlorhexidine is broad spectrum and could be bactericidal or bacteriostatic depending on the concentration

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16
Q

Cultivating in an anaerobic or aerobic environment will grow the most intra oral microbes

A

Anaerobic

17
Q

What could be added to Mitis -Salivarius growth medium to make it selective for Streptococcus mitis or Streptococcus salivarius?

A

Tellurite. Growth of mitis

18
Q

What agar grows candida

A

Sabouraud agar

19
Q

What bacteria causes sore throat and inflamed pharynx

A

Streptococcus pyogenes

20
Q

Which carbohydrate is fermented in the Snyder test?

A

glucose

21
Q

what is germination

A

the process of reactivation of spore form to vegetative form

22
Q

what does Clavulanic acid do

A

Inactivates beta lactamase to prevent bacteria inhibiting the beta lactam in antibiotics. Combined with pencillins to prevents antibiotic resistance.
[Co-amoxiclav]

23
Q

name some antibacterial toothpaste ingredients

A

Chlorhexidine, essential oils, tannous fluoride, Triclosan, Cetylpyridium chloride

24
Q

name 2 spore forming species

A

clostridium and bacillus

25
Q

When culturing microorganisms on agar plates, why is it important the plate is placed in the incubator top down.

A

To stop condensation settling on the agar surface

26
Q

What is a virulence factor

A
  • features of or molecules produced by bacteria, viruses, fungi and protozoa
  • Help pathogenic microorganisms to (1) invade the host, (2) cause disease, and (3) evade host defences
27
Q

What does a leukotoxin do and what bacteria is it produced by

A
  • Toxic to leukocytes
  • A type of exotoxin
  • Aggregatibacter actinomycetemcomitans
28
Q

the 3 components of an enveloped virus

A
  • Nucleocapsid - Nucleic acid (DNA or RNA) and protein shell

- Lipid layer from host with envelope glycoproteins / spike proteins

29
Q

What effect would incubating sub gingival plaque bacteria anaerobically be on the number of colonies which formed?

A

There would probably be more cfu. The reason is that the nearly all the bacteria in the mouth are either facultatives (do not need oxygen but can grow in its presence) or strict anaerobes. So, a plate incubated aerobically will only grow the facultatives whereas a plate incubated anaerobically will grow the facultatives as well as the anaerobes. However, there are some strict aerobes that would not grow anaerobically, so it is not clear cut.

30
Q

what bacteria used in Snyder test. What pH is the growth medium

A

lactobacilli
pH 5
fermenting glucose and making lactic or acetate acid

31
Q

Why the number of CFU may not be the same as the number of cells in a culture

A
  • Some cells may be dead/non viable
  • Some may be unable to grow on the particular medium
  • cells often tend to clump or form chains and, if not dispersed, multiple cells will make a single CFU.

Microbiology for dentists (5 decks)

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