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IOE Dentistry - Oral Microbiology > The Resident Oral Microbiota > Flashcards

The Resident Oral Microbiota Flashcards

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1
Q

What is plaque?

A

The community of microorganisms found on the tooth surface as biofilm embedded in a matrix of polymer of salivary and bacterial origin

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2
Q

What do you call plaque found on the fissures of teeth?

A

Fissure plaque

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3
Q

How much bacteria can be in fissure plaque?

A

1-33 x10^6

1,000,000-33,000,000

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4
Q

What do you call plaque found on the side of the tooth?

A

Approximal plaque

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5
Q

What do you call plaque found on the gingival of the teeth?

A

Sub ginigival plaque

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6
Q

How much bacteria can be found in sub gingival plaque?

A

10^3 - 10^6

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7
Q

Why do plaque found in different sites of the mouth have different characteristics

A

Because the mouth offers varying conditions at different sites in the mouth so only certain bacterial species can survive in certain environments

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8
Q

How much bacteria can be found in the saliva

A

Up to 10^9 bacteria per mL

1,000,000,000

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9
Q

How much bacterial can be found on the tongue?

A

100 bacteria

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10
Q

What was the first thing microbiologist do to identify oral bacteria?

A

They tried to isolate the microbes and grow them in a liquid or solid medium

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11
Q

Give an example of a solid medium microbiologist may have used to grow microorganisms

A

Agar (soft solid) where you can subculture bacteria on the surface and they use the nutrients in the agar to grow

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12
Q

How many types of growth media and what are they?

A

2 types:

  1. Selective
  2. Non selective
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13
Q

What is a non selective medium

A

It contains as many nutrients as possible for microbes to grow

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14
Q

What is a selective medium

A

Creating an environment for only a specific micro organism to grow
Requires you to do further research on specific microorganisms to see what conditions are favourable to them

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15
Q

Give some examples of non selective medium

A

Blood agar has horse and/ or sheep blood

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16
Q

Give some examples of deceive mediums

A

Mitis salivarius bacitracin agar allows only mutants streptococcus to grow

Sabouraud agar only allows yeast to grow

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17
Q

What determines the gram reaction of bacteria

A

Its cell wall

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18
Q

What is the cell wall of bacterial made of?

A

peptidoglycan

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19
Q

What is the main difference between prokaryotes and eukaryotes

A

Prokaryotes don’t have a nucleus so their generic material just floats around as plasmids in the cell

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20
Q

What is the DNA coiled into in bacteria

A

A circular double stranded nucleoid

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21
Q

What is the cytoplasm

A

A viscous substance that fills in the entirety of the cell and it is packed with ribosomes

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22
Q

What is a flagellum

A

A tail like extension on some bacteria

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23
Q

How can we identify different bacteria?

A 
Using differential characteristics like: 
Gram stains 
Morphology 
Haemolysis 
Pigment
Metabolic activity 
Antigens 
Cellular composition 
Nucleic acid
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24
Q

Why are not all bacteria cultivable in a lab

A

Because we are unable to reproduce the unique requirements that each bacterial species may have to grow and multiply

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25
Approximately how many oral bacteria species are we capable of growing in the lab?
70%
26
What do all bacteria have
A plasma membrane surrounded by a cell wall made up of peptidoglycan
27
What does it mean if a bacteria is described as being gram-positive
The peptidoglycan on the outside of the cell wall is very thick There are lipoteichoic acids that transverse and anchor into the membrane
28
What does it mean if a bacteria is described as being gram-negative
They have a thinner peptidoglycan layer on the outside of their cell wall It has a second phospholipid bilayer on the outside of the peptidoglycan later This second phospholipid bilayer has lipopolysaccharides (O antigens) and lipid A which are very unique to the gram negative
29
What do lipopolysaccharides (O antigens) and lipid A do?
They are recognised by host cells and may be involved in triggering the defence mechanisms and triggering inflammation
30
Describe how you would carry out gram staining
1. You’d take a sample of a colony using a serile loop and you make a smear on a glass slide 2. You let that dry using a Bunsen layer 3. The heat fixates the cells into the glass slide 4. Use a crystal violet dye to flood that glass slide for a minute 5 Rinse 6. Then use iodine which will foxate the crystal violet within the peptidoglycan layer 7. Decolorisation using acetone (or any type of alcohol) 8. Add a counter stain (usually safranin) that will should stain everything pink Gram positive cells: will be purple Gram negative cells: will be pink
31
What result will a gram positive bacteria give during gram staining and at what stage?
A gram positive cell will go purple when alcohol (like acetone) is added This is because the iodine will have fixated the crystal violet into the peptidoglycan and so the acetone will not decolorise the sample
32
What result will a gram negative bacteria give during gram staining and at what stage?
When acetone is added a gram negative bacteria will go white This is because it has a second philolipid membrane that covers the thin peptidoglycan So the crystal violet will not be fixated into the peptidoglycan layer. The crystal violet will be completely washed off and so the cells will be completely decolourised
33
If lipoteicholic acids are found in a bacteria cell what type of gram staining will it give
Positive
34
Where are lipoteicholic found in the cell
They are transverse and anchor into the membrane
35
How do staphtococci divide? And what gram stain do they give?
On multiple planes in clusters | They are gram positive
36
How do streptococci divide?
On one plane in chains
37
If you carry out a gram staining test and at the end the sample is a pink colour what type of bacteria do you have
Gram negative
38
How can cell morphology be used as a differential characteristic to differentiate between bacterial cells
``` Bacteria have many different shapes such as Rods Cocci Coccobacilli Curved rods (vibrio) Spirilla ```
39
How can colony morphology be used as a differential characteristic to differentiate between bacterial cells
As bacterial colonies can have different: Shapes Pigments Haemolysis
40
What are the different haemolysis? | And what is haemolysis?
There are three types of haemolysis: Alpha (oxidation of the haem in iron) Beta Gamma Haemolysis helps you see if the bacteria produces the haemolytic enzyme that helps them to destroy specific substrates
41
What would you see if a bacterial colony was alpha haemolytic?
A greenish tint would appear on top of the colony
42
What would you see if a bacterial colony was beta haemolytic?
You would end up with zones of clearing as the haemolytic enzymes completely destroy the haem groups
43
What would you see if a bacterial colony was gamma haemolytic?
There’s no hydrolysis
44
How can metabolic activism be used as a differential characteristic to differentiate between bacterial cells
Certain types of bacteria may produce unique enzymes to help them in fermentation Some enzymes may produce unique acids or gases Or some bacteria may utilise certain carbohydrates or proteins
45
How can antigens be used as a differential characteristic to differentiate between bacterial cells
Some bacteria may present specific antigens that we can use to detect them
46
How can cellular composition be used as a differential characteristic to differentiate between bacterial cells
Like gram staining shows us the type of peptidoglycan | You could test for unique lipids or amino acids that bacteria may have
47
How can DNA be used as a differential characteristic to differentiate between bacterial cells
Where dna is extracted from the cell | It is the most accurate way of identifying bacteria
48
What are the main groups of gram positive bacteria found in the mouth
1. Cocci :Streptococcus | 2. Rods: Actinomyces, Eubacterium, Lactobacillus
49
What are the main groups of gram negative bacteria found in the mouth
Cocci: Neisseria, Veillonella Rods: Aggregatibacter, Fusibacterium, Prevotella, Treponema
50
What is the plural of genus?
Genera
51
Name the main gram positive cocci found in the mouth
``` Streptococcus Oralis (found in health) Streptococcus mitis (found in health) Streptococcus sanguinis (found in health) Streptococcus intermedius (found in abscesses) Streptococcus mutans (found in dental caries) Streptococcus sobrinus (found in dental caries) ```
52
How can Streptococcus sanguinis be found in the heart and what is the effect of this?
They can travel through the blood stream to the heart and colonise there They make biofilm in the heart which can lead to heart disease and heart attack
53
Which bacteria are the early colonisers of the mouth
Streptococci salivarius
54
Which bacteria is catalase negative specific to
Streptococci oralis
55
What does the catalase negative enzyme do?
Degrade hydrogen peroxide into water and hydrogen | This is v beneficial as hydrogen peroxide is very dangerous to bacteria
56
How can hydrogen peroxide be used to differentiate between streptococci bacteria?
Add hydrogen peroxide to the glass slide and if bubble of oxygen appear you have a catalase positive result If no bubbles appear then you have Streptococcus oralis
57
Name some gram positive rod bacteria
Actinomyces Lactobacillus Eubacterium
58
Where is Actinomyces commonly found?
Dental plaque Implicated in root surface caries They are opportunistic pathogens They are gram positive branches rods
59
Describe Eubacterium
They are gram positive rods and filaments They are difficult to grow in the lab They are found in plaque
60
Describe lactobacillus
They are gram positive rods Implicated in advanced dental caries They are acidoogenic
61
Name some gram negative bacteria
Neisseria Veillonella Treponema Fusobacterium
62
Describe Neisseria
They are gram negative coccus | Early colonisers of the tooth
63
Describe Veillonella
They are gram negative coccus Prefer anaerobic conditions Utilise lactic acidosis is plaque
64
Describe treponema
They are gram negative Strictly anaerobic Found in sub gingival plaque Implicated in periodontal disease
65
Describe fusobacterium
They are gram negative filaments Anaerobic Common in plaque They are key bridging organisms between early and late colonisers
66
How can we identify bacteria that we can’t culture
We use DNA analysis
67
What is the method of choice of microbiologist for dna analysis of bacteria
The 16S ribosomal RNA gene (16srRNA)
68
Why can we use the 16S ribosomal RNA gene?
As eukaryotes have different RNA To prokaryotes (they are different sizes and so have a different gene sequence ) Prokaryotes ribosomes have two sub units large and small We are interested in the small 16S supplement that codes the 16S ribosomal RNA gene Scientists found that this gene has really interesting properties It is about 1500base pairs long and it has different regions
69
What interesting properties does the 16S ribosomal RNA gene have?
It is about 1500base pairs long and it has different regions and the conserved regions are the same for every 16s rna ribosomal Gene
70
What are the different regions of the 16S ribosomal RNA gene?
The conserved region (the same for every 16S rna ribosomal gene in every prokaryote) Variable region
71
How can we use the 16S ribosomal RNA gene?
Extract the dna Amplify the 16s gene using PCR and then sequence it Then compare it to the online database The closer related the organisms are the more similar their variable region
72
How many phylotypes have been detected in the mouth using the 16S rRNA gene sequencing?
Around 700 phylotypes (species Around 400 of these are in the sub gingival domain Around 35 have not yet been cultured
73
What’s another word for species
Phylotypes
74
Name some molecular typing methods
16A rRNA gene amplification FISH Denaturing gradient gel electrophoresis (DGGE) DNA-DNA Checkerboard Human oral microbe identification microarray (HOMIM) Most of these are obsolete and the one preferred by scientists now a days is: Next generation sequencing
75
What can you say if a green tint is seen on a bacterial colony
It displays alpha haemolysis
76
If there’s no hydrolysis what type of haemolysis does the bacterial colony display
Gamma haemolysis
77
If there are clear zones in the bacterial colony what can you say about its haemolysis
It displays beta haemolysis
78
Streptococci salivarius are described as what type of colonisers?
Early colonisers
79
Streptococci oralis are the only bacteria that have which enzyme
Catalase negative

IOE Dentistry - Oral Microbiology (5 decks)

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