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IOE > Microbiology > Flashcards

Microbiology Flashcards

Learn about the microbiology section of IOE

1
Q

What is the resident microbiota

A

Complete set of microbes that occupy the healthy body site

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2
Q

What is the human microbiome?

A

All the microbes associated with the human body

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3
Q

Name 6 areas microbial communities in the body

A

Mouth, Skin, axillary, stomach, UI tract, intestine

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4
Q

What is one of the main differences between human microbiota and microbiome?

A

The microbiome contains genetic material as well

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5
Q

How man microbes are there in 1ml of saliva?

A

10^8

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6
Q

What size are eukaryotes? (Fungi, Protozoa)

A

10-100ųm

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7
Q

What size are viruses?

A

50-100nm

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8
Q

Why are viruses non cellular? (And still alive)

A

Enveloped by a protein coat, not a phospholipid bilayer so technically not a cell

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9
Q

Define Classification

A

Arrangement into taxonomic groups based on similarities or relationships

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10
Q

In taxonomy, what is the smallest rank?

A 
Strain.
-family
-genus
-species
-strain 
Specific strains will have different genes which e.g. can cause virality
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11
Q

What is plaque?

A

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

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12
Q

Name 6 out of the 8 benefits of the resident microbiota

A

[All 8 are given]

  • competitive exclusion of exogenous pathogens
  • antagonism of exogenous pathogens
  • promotion of normal development of immune system
  • promotion of normal human cellular physiology and nutrition
  • enhancement of epithelial barrier function
  • disease follows dis-regulation or imbalance
  • certain bacteria actively modulate immune to prevent chronic over-stimulation
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13
Q

Name the 4 main distinct sites for oral colonization

A

Teeth, saliva, mucosal surfaces, Gingival Crevicular Fluid (GCF)

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14
Q

What is the name of the process that keeps mucosal colonisation relatively low?

A

Desquamation : the shedding of the outer layer if the epithelium

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15
Q

Why can teeth allow plaque to accumulate

A

It is non-shedding, so the colonizing on the surface can remain

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16
Q

True or false: on a single tooth, there is more than one environment/conditions for microorganisms

A

True

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17
Q

Name two liquids in the mouth that can influence where microorganisms colonise and why.

A

Saliva:

  • glyoproteins
  • host defenses
  • buffering role

GCF:

  • serum like exudate
  • phagocytic cells
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18
Q

What is the temperature of the oral cavity?

A

It remains fairly constant at 30, up to 36°C

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19
Q

How does redox potential influence microbiology in the oral cavity?

A

It works as a factor in colonisation, it ifluences the type of organism that will be found at a particular site

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20
Q

What is the main immunoglobulin in GCF

A

IgG

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21
Q

What is the main immunoglobulin in GCF11

A

IgA

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22
Q

True of false: the mouth is a non-selective environment

A

False

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23
Q

Define symbiosis

A

Close mutually beneficial relationship between two dissimilar orgnanisms

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24
Q

What is mutualism?

A

An association between 2 organisms where both partners derive benefit

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25
Q

What is commensalism?

A

A relationship between 2 dissimilar organisms where one gains benefit, the other is unaffected (no harm done)

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26
Q

What is parasitism?

A

One organisms derives benefit, one is harmed in a relationship between 2 organisms

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27
Q

What is a pathogen

A

A microbe capable of causing disease

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28
Q

What is an opportunistic pathogen?

A

An organism that is a member of the resident oral microbiota that causes infection under certain circumstances

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29
Q

Describe dysbiosis

A

Imbalances in the resident human microbiota, or our responses to them

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30
Q

Name 5 out the 7 factors that can lead to opportunistic infection

A

[All 7 given]

  • damage to epithelium
  • presence of foreign body
  • transfer to other body site
  • suppression of immune system
  • disruption of normal microbiota
  • unknown precipitating factor
  • impairment of host defenses by exogenous pathogens
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31
Q

Name the 3 bacteria that are involved in caries

A
  • streptococcus mutans
  • Lactobacillus spp.
  • actinomyces spp.
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32
Q

Name the 4 bacteria involved in periodontal disease.

A
  • Porphyromonas gingivalis
  • Tannerella forsythia
  • Spirochaetes
  • Aggregatibacterium actinomycetemcomitans
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33
Q

Which 3 bacteria are involved in oral abscesses?

A
  • streptococci
  • actinomyces
  • gram-negative anaerobes
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34
Q

Describe how a bacteria may find nutrients

A

Chemotaxis (movement of an organisms towards an chemical substance)

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35
Q

What is catabolism?

A

The breakdown of large molecules into smaller, more manageable ones which can be processed

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36
Q

What is anabolism?

A

The biosynthesis and construction of large molecules from small units

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37
Q

What do bacteria do when there are no sugars available?

A

They do Asaccharolytic metabolism, where proteins and peptides are used (broken down)

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38
Q

How many ATP are produced for 1 molecule of glucose during fermentation from bacteria?

A

2

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39
Q

Name 3 fermentation pathways.

A

Homolactic acid, Heterolactic acid, Ethanolic, Propionic, Butanediol, Amino acid

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40
Q

In the food chain, streptococcus can metabolize glucose to lactate. What can Veillonella do?

A

Metabolize lactate into acetate and propionate, turning a strong acid into a week acid leading to less caries

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41
Q

What is the first thing onto the tooth to start the biofilm?

A

The salivary pellicle, which makes the tooth sticky for bacteria to attach

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42
Q

What is the name of the group of organisms that are the first to colonise an area (succession)

A

Pioneer species

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43
Q

Name 3 different types of plaque (by location)

A

Fissure plaque, approximal/supragingival plaque and sub-gingival plaque

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44
Q

What is a non-selective media?

A

The composition of the medium will allow the growth of as many organisms as possible

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45
Q

What is a selected media?

A

A medium which contains nutrients which enhance the growth of specific species and may have nutrients to inhibit growth of unwanted species

46
Q

What is a bacterial cell wall made out of?

A

Peptidoglycan

47
Q

What is a nucleoid?

A

The region of a prokaryotic cell which contains the loose, coiled, protein associated, double stranded DNA

48
Q

Roughly how many organisms in the mouth are actually culturable?

A

About 50%, because the lab cannot replicate/don’t know the right conditions and nutrients for some of the organisms to grow in a lab environment

49
Q

How many steps are involved in gram staining?

A

5

50
Q

What is the first step of gram staining?

A

Take a sample from a grown colony and make a smear on a glass slide

51
Q

What is the second step of gram staining?

A

Stain with crystal violet

52
Q

What is the third step of gram staining?

A

Stain with iodine

53
Q

What is the fourth step of gram staining?

A

Decolourise with acetone

54
Q

What is the fifth step of gram staining?

A

Counter-stain with safranin

55
Q

What is the colour for a gram-positive result?

A

Purple

56
Q

What is the colour for a gram-negative result?

A

Pink

57
Q

How does gram staining work?

A

The addition of crystal violet will attach to the cell membrane. Acetone dehydrates the sample, shrinking the peptidoglycan layer, tightening it so the stain is locked. Without a cell wall like this, the outer membrane is degraded and the colour is lost, so it is counter-stained with safranin.

58
Q

Why does the addition of safranin not change the colour of gram-positive bacteria?

A

As the pink is lighter than the purple, the darker colour will shine through so it will still look purple.

59
Q

What gram result are streptococci?

A

Positive (purple)

60
Q

What shape is a ‘cocci’ bacteria?

A

Circular

61
Q

What shape is a coccobacilli bacterium?

A

Oval

62
Q

What property is used in haemolyis?

A

An enzyme that can be produced by certain bacteria than can cause hameloysis (break down blood cells)

63
Q

What medium is used in haemolyis?

A

Blood agar

64
Q

What is the result of alpha-haemolysis?

A

The iron in the haemoglobin is oxidized, leading to a green shine on the agar plate with partial lysis

65
Q

What is the result of beta-haemolysis?

A

The enzymes cause a complete rupture of the red blood cells contained in agar, leading to large zones of clearing

66
Q

What is the result of gamma-haemolysis?

A

There is no lysis whatsoever

67
Q

True of false: you could use a specific metabolic process (and its outcome) to help determine a colony

A

True.

68
Q

What gram-stain, shape and haemolyis are the oral streptococci bacterium?

A

Gram-postive, cocci, Alpha-haemolytic

69
Q

What is the catalase test for identification of a colony?

A

Cataalse in an enzyme that can hydrolyse hydrogen peroxide into water and oxygen
A negative result means it cannot break down hydrogen peroxide, vice versa for opposite.

70
Q

Are streptococcus catalase negative or positive?

A

Negative

71
Q

Describe the gram stain and characteristics of:

Actinomyces

A

Gram +ve
Branched rods
Common in plaque
Opportunistic pathogens

72
Q

Describe the gram stain and characteristics of:

Lactobacillus

A

Gram +ve
Rod
Implicated in advanced caries

73
Q

Describe the gram stain and characteristics of:

Eubacterium

A

Gram +ve
Found in plaque
Difficult to grow in a lab

74
Q

Describe the gram stain and characteristics of:

Neisseria

A

Gram -ve
Aerobic
Early colonisers of the tooth

75
Q

Describe the gram stain and characteristics of:

Veillonella

A

Gram -ve
Coccus
Anaerobic
Utilises lactic acid in plaque

76
Q

Describe the gram stain and characteristics of:

Treponema

A

Strictly anaerobic

Implicated in periodontal disease

77
Q

Describe the gram stain and characteristics of:

Treponema

A

Strictly anaerobic

Implicated in periodontal disease

78
Q

Describe the gram stain and characteristics of:

Fusobacterium

A

Gram-ve
Filament
Anaerobic, common in plaque
Bridging organisms (think fuse) in succession

79
Q

How do bacteria divide?

A

Binary fission

80
Q

Describe the total count method to measure growth

A

Measure microbes in a given sample (e.g. 1ml of saliva)
Place onto a glass square
Then count the number of cells in server boxes and average
(Microscope version of taking a quadrat)

81
Q

What is a problem with the counting chamber method?

A

You cannot tell if the cells you are counting are alive or dead

82
Q

How does the viable method for counting bacteria work?

A

Take e.g. 1ml of saliva, culture it on an agar plate, do a serial dilution (making it more and more dilute each time with a sterile broth/medium) and culture the dilution. Then count the colonies and scale back up again

83
Q

What do you require to culture viruses?

A

Living host cells to support viral replication

84
Q

Name the 4 phases in bacteria growth curves

A

Lag, exponential, stationary, death/decline

85
Q

What happens during the lag phase of bacterial growth

A

The bacteria arent multiplying, still metabolically active, time taken to adjust to surrounding conditions

86
Q

What happens during the log phase of bacterial growth?

A

The bacteria divide rapidly, doubling each division with the lots of available resources

87
Q

What happens during the stationary phase of bacterial growth?

A

Nutrients levels decrease, waste products build up. Cell death is equal to cell replication

88
Q

What happens during the death phase of bacterial growth?

A

Run out of nutrients, increasing toxic waste, more bacteria are dying than are being created by division

89
Q

What is the temperature of the mouth?

A

35°C, can raise to 39 during infection

90
Q

What are psychrophiles?

A

Organisms that grow in cold temperatures (optimum is around 20°C)

91
Q

What are mesophiles?

A

Organisms that can grow in moderate temperatures, with an optimum temperature of around 37°C (think me -> medium)

92
Q

What are thermophiles?

A

Organisms that can grow in high temperatures, with an optimum of around 70°C (think thermo, as in hot)

93
Q

What are obligate aerobes?

A

Organisms that only grow in the presence of high concentrations of oxygen

94
Q

What are Facultative anaerobes?

A

They are tolerant to any kind of O2 concentration, will grow anywhere

95
Q

What is a microaerophile?

A

An organism that thrive only at just lower than atmospheric concentrations of oxygen

96
Q

What is an aerotolerant anaerobe?

A

An organism that can tolerate small amounts of oxygen but function without oxygen

97
Q

What are obligate aerobes?

A

Organisms that require no oxygen at all to survive

98
Q

What redox potentials do anaerobes prefer?

A

Reduced conditions (low potential)

99
Q

How does plaque redox change over time?

A

First high because high in oxygen, over a couple days more electrons are gained to the RP decreases, allowing the promotion of more anaerobic bacteria

100
Q

What is the 1st stage of biofilm formation?

A

Within seconds, a surface gets covered in a film of proteins and glyoproteins (acquired pellicle)
Also called conditioning film

101
Q

What is the 2nd stage of biofilm formation?

A

Passive transport of microbes to the follicle via the flow of saliva.

102
Q

What is the 3nd stage of biofilm formation?

A

Reversible stage

The bacteria are held by very weak, long range forces (e.g. van der Waals, ionic attraction)

103
Q

How thick is the conditioning film, and what is it derived from?

A

Up to 1um thick

Mostly from saliva, can also have parts from the GCF and the microbes themselves

104
Q

What is the 4th stage of Biofilm formation?

A

Irreversible stage
Short range, specific, strong interactions caused by complementary molecules on the bacteria that bind to the proteins on the pellicle
They become the early pioneer colonisers

105
Q

What is the 5th stage of biolfilm formation?

A

Co-adhesion
Where different microbes bind to the primary colonisers, doesn’t have receptors complimentary to pellicle but do to the microbes already attached

106
Q

Why dont the microbes just bind to the saliva proteins that make the pellicle in solution?

A

When the proteins attach, they unwind/change shape, exposing their binding sites

107
Q

What is the plaque matrix?

A

Sticky polymers produced by both the host and the bacteria that make up around 30% of the plaque volume
Can have proteins, fructans, glucan, extra cellular DNA

108
Q

Describe 6 functions of the plaque matrix

A
  • protection from the environment and host defenses
  • nutritional reserve
  • structural support to the biofilm
  • interacts with molecules
  • water retention
  • retards penetration of antimicrobials
109
Q

True of false: all reactions between microbes in the biofilm are synergistic and beneficial.

A

False

110
Q

True of false: you can have altered gene expression when microbes are in a biofilm

A

True

111
Q

What is MIC?

A

Minimum Inhibitory Concentration

The smallest concentration that inhibits growth (doesn’t necessarily kill)

112
Q

What is MBC?

A

Minimum Bactericidal Concentration

The minimum concentration needed to kill a bacteria (measure of antimicrobial resistance)

IOE (3 decks)

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