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Stage 2 Microbiology for dentists > MFD.07 > Flashcards

MFD.07 Flashcards

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Biology 101 flashcards
1
Q

Describe a planktonic culture of cells

+e.g.

A

homogenous (same nutrients throughout &species) , single species, nutrient rich, • Uniform growth rate
• Even distribution of O2, nutrients, waste etc
• Cells well-separated
• No extracellular matrix
e.g. in a beaker

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2
Q

Describe a surface-associated culture of cells

+e.g.

A

limited heterogeneity, single species, nutrient rich e.g. petri dish

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3
Q

Describe a natural culture of cells

+e.g.

A

heterogenous, mixed species, nutrient limited e.g. clay wall

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4
Q

What is a biofilm?

A

A community of microbial cells encased within a matrix of polymers and associated within an interface. In nature, most bacteria grow in biofilms.

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5
Q

Give an example of a heterogenous culture?

A

biofilm

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6
Q

Compare species of planktonic culture vs “natural” growth:

A

planktonic: single species
other: mixed

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7
Q

Compare growth rate of planktonic culture vs “natural” growth:

A

planktonic: uniform
other: mixed

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8
Q

Compare distribution of O2, nutrients, waste etc of planktonic culture vs “natural” growth:

A

planktonic: even
other: uneven

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9
Q

Compare position of cells of planktonic culture vs “natural” growth:

A

planktonic: well-seperated
other: in close contact

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10
Q

Give an example of “Natural” growth

A

biofilm

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11
Q

True or false

Bacteria in biofilms from those in broth cultures.

A

true

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12
Q

Compare resistance to antibiotic of biofilm bacteria and planktonic cells

A

biofilm bacteria are 1000 times more resistant then planktonic

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13
Q

Can bacterial communities be more pathogenic than pure cultures?

A

yes

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14
Q

Why is there such a range of bacteria in biofilms?

A

1) Hides most bacteria from host immune system

2) provides niches e.g. anaerobic environments

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15
Q

Where are biofilms found?
(3)
e.g.*3 e,g. location

A

Anywhere where there is:
An interface
Moisture
Nutrients/energy source
e.g.
Air-liquid interfaces, surfaces of ponds, oceans
Air-solid interfaces, tree trunks, rocks, soil particles
Solid-liquid interfaces, internal surfaces of pipes(including dental unit waterlines), catheters, teeth

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16
Q

What are the 4 stages of a biofilm?

A
  1. attachment ( adhesion of a few motile cells to a suitable solid surface)
  2. colonization (intercellular communication, growth, and polysaccharide formation)
  3. Development (more growth and polysaccharide
  4. Active Dispersal (triggered by environmental factors such as nutrient availability)
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17
Q

Why are nutrients non-uniformly distributed in a biofilm?

A

the matrix impedes mass transfer

18
Q

What forms the biofilm matrix?

A

macromolecules from the basic structure and small molecules are trapped within matrix

19
Q

What macromolecules form the basic structure?

A

polysaccharides, proteins,nucleic acids

20
Q

What small molecules may trapped within the matrix of a biofilm?

A
  • Nutrients
  • Metals
  • signalling molecules
21
Q

What are the 4 diagnostic tools to proving a biofilm infections?

A

• Pathogenic bacteria are associated with a surface.
• Direct examination of infected tissue demonstrates aggregated cells in cell
clusters encased in a matrix, which may be of bacterial and host origin.
• Infection is confined to a particular site in the host.
• Recalcitrance to antibiotic treatment despite demonstrated susceptibility of
planktonic bacteria. (planktonic bacteria are less susceptible to antibiotic when in biofilm)

22
Q

Recalcitrance basically means the same as…

A

reistance

23
Q

Why are biofilm bacteria so resistant?

A
  • Slow growing
  • Presence of dormat (“persister”) cells
  • Sequestration (=seperation) from the immune system
  • Elevated expression of efflux pumps.
  • Poor penetration of antibiotics.
24
Q

What type of antibiotic is effected by the fact that biofilm bacteria are sequestered from the immune system?

A

bacteriostatic antibiotics that work in conjunction with host immunity)

25
Q

define efflux pumps

A

A cell membrane protein channel that selectively admits or excludes chemicals from the cytoplasm. In some bacteria efflux pumps prevent their cells from accumulating antibiotics, contributing to drug resistance.

26
Q

Does antibiotic resistance vary with stage of growth of synchronous populations of cells in a biofilm?

A

yes

27
Q

1) Growth may play a role in antibiotic resistance, what evidence is there against this?
2) what does this mean?

A

1) slow-growing cells in biofilms are not more resistant to RNA synthesis inhibitors,
2) probably not just growth rate that matters,

28
Q

Why is there a difference between MIC and MBC in a biofilm or planktonic populations of cells?

A

as dormant/inacitve cells (persister cells) are present,

they are difficult to kill with antibiotics

29
Q

What does MIC stand for? what does it mean?

A

MIC= minimum inhibitory concentrations ( minium ammount needed to inhibit growth

30
Q

WHat does MBC stand for? what does it mean?

A

MBC= minium bactericidal population

the lowest concentration of an antibacterial agent required to kill a particular bacterium

31
Q

What may be responsible to infections on replacement hips 10-15 years after an operation?

A

SVC
Dormant cells in a biofilm, can become a significant proportion of biofilm, these form small colonies on agar (small colony variants, SCVs).

32
Q

What is a new method (not yet on clinic) of administering antibiotic to tackle small colony variants ( dormant cells in a biofilm)?

A

adding nutrients along with the antibiotic

33
Q

What 2 things about the cells in particular that can make a biofilm more resistant to antibiotic?

A
  1. persister cells (dormant cells)
  2. slow growth rate cells
  3. Elevated expression of efflux pumps
34
Q

Why are biofilms highly resistant to phagocytosis?

A
  • inflammatory cells cannot penetrate the matrix

- even if they do penetrate channels, they do not ingest bacteria effectively

35
Q

How do biofilms resist an immune attack?

A
  1. Biofilms are highly resistant to phagocytosis.
  2. Antibodies (IgG) penetrate poorly.
  3. Adaptive responses in biofilms or communities can protect bacteria.
  4. Up-regulation of efflux pumps
36
Q

Give 3 examples of adaptive immune responses bacteria have in a biofilm when immune evasion occurs? ( you don’t need to recall bacteria name)

A
  • Pseudomonas spp. produce rhamnolipids in biofilms, which can kill neutrophils
  • Interactions with oral streptococci induce production of a complement-evading protein by Aggregatibacter actinomycetemcomitans
  • Up-regulation of efflux pumps
37
Q

Antibiotic efflux pumps are up-regulated in biofilms formed by (adaptive immune response):
(3)

A
  • E. coli
  • P. aeruginosa
  • Candida albican
38
Q

Diffusion is impeded by the biofilm, but:

A
  • This is not significant for small molecules.
  • Even large molecules such as IgG (~150 kDa) are only weakly limited.
  • Molecules are carried through water channels.
39
Q

What 2 ways, other than the limit on diffusion, is mass transport controlled by the bacterium;
+E.G.

A
  1. Electrostatic or van der Waal’s interactions are much more important – the matrix acts as an ion exchange resin e.g. metal cations become trapped in the anionic matrix. E.g. tobramycin binds to extracellular DNA found naturally in biofilms, impeding penetration by the antibiotic
  2. Reaction is also important. Reactive molecules such as peroxide are inactivated by the matrix.
40
Q

How are biofilms relevant in dentistry?

A
  1. Cross-contamination

2. Dental plaque ( a biofilm found in the mouth dur)

41
Q

How are biofilms relevant in dentistry?

A
  1. Cross-contamination (surfaces in the clinic and in dental unit waterlines)
  2. Dental plaque ( a biofilm found in the mouth dur)

Stage 2 Microbiology for dentists (25 decks)

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