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Microbial world > Lecture 9 and 10 > Flashcards

Lecture 9 and 10 Flashcards

1
Q

What was Louis Pasteur investigating when he discovered pasteurisation?

A

Fermentation (wine preservation)

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2
Q

What did Pasteur discover among the yeast?

A

Bacteria

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3
Q

What theories did Pasteur have?

A

Germ theory: cells germinate, cause spoilage

Germs could be killed by heat to prevent spoilage

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4
Q

Who is the ‘father of antispetic surgery’?

A

Sir Joseph Lister

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5
Q

What did Joseph Lister do?

A

Disinfection of wounds/hands/surgical instruments/rooms using carbolic acid (phenol)

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6
Q

Who discovered penicillin?

A

Alexander Fleming

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7
Q

What bacteria produces inhibitory substance penicillin?

A

Penicillium notatum

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8
Q

How does penicillin kill?

A

Interfering with cell wall production which ruptures as E.coli size grows

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9
Q

Who developed a method to extract large amounts of penicilin from the mould?

A

Sir Ernst Chain

Lord Howard Florey

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10
Q

Define sterilisation

A

Removal of all forms of microbial life

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11
Q

How are things sterilised?

A

Pressured steam/gas

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12
Q

What is commercial sterilisation?

A

Sufficient heat to kill Clostridium botulinum endospores in canned food

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13
Q

What is disinfection?

A

Destruction of vegetative pathogens on inaminante objects

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14
Q

What is antisepsis?

A

Destruction of vegetative pathogens on living tissue

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15
Q

What is degerming?

A

Removal of microbes from a limited area

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16
Q

What is sanitisation?

A

Lowering microbial counts on eating/drinking utensils

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17
Q

What is biocide/germicide?

A

Kills microorganisms

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18
Q

What is bacteriostasis?

A

Inhibition of growth/multiplication of bacteria

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19
Q

What name is given to the length of time it takes for 90% of the population to be killed?

A

Decimal reduction time

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20
Q

What are three methods of action of microbial control agents?

A
  • Alteration of membrane permability
  • Damage to proteins
  • Damage to nucleic acids
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21
Q

Give an example of damaging nucleic acids.

A

UV causes thymine dimers to form

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22
Q

What is the main type of bacteria that produces endospores?

A

Gram positive bacteria living in the soil

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23
Q

Why do soil bacteria produce endospores?

A
  • Soil environment can’t be controlled
  • Competition
  • Environment can dry out etc.
24
Q

How can microbial control agents be evaluated?

A

Use- dilution test

Disk diffusion method

25
Q

How is the use-dilution test carried out?

A 
Dip metal carries in test bacteria and dry
Place in control agent
Incubate (10 mins) at 20C
Place carriers in growth medium
Incubate 48 hours
Number of cultures that grow
26
Q

What is disk diffusion method?

A

Disks soaked in control agent placed on agar with test bacteria, measure zone of inhibition

27
Q

What name is given to the lowest temperature at which all microorganisms in a liquid are killed in 10 minutes?

A

Thermal death point

28
Q

What is thermal death time?

A

Minimal length of time all microorganisms in a liquid are killed at a given temperature

29
Q

What is decimal reduction time?

A

Time required to kill 90% of the micoorganisms

30
Q

What is the temperature used in an autoclave?

A

121C

31
Q

What is the pressure in an autoclave?

A

15psi

32
Q

How long is an autoclave run for?

A

15min for 10ml volume

33
Q

What can’t an autoclave kill?

A

Prions

34
Q

What temperature and time is required for pasteurisation?

A

72C for 15 seconds

35
Q

What is the temperature and time for ultra high-temperature treatment (UHT)?

A

140C for 4 seconds

36
Q

What are phenolics?

A

Derivative of phenol, less irritating

37
Q

How do phenolics work?

A

Destroy lipids in cytplasmic membrane

38
Q

How does triclosan (a phenolic) work?

A

In soaps/toothpaste etc.

Inhibits enzyme for lipid biosynthesis

39
Q

Name a chemical agent for microbial growth that has a broad spectrum of activity

A

Biguanides (chlorhexidine)

40
Q

What does chlorhexidine not work against?

A

Psyedomonads (Gram negative)

Endospores

41
Q

What halogens are used to control microbial growth?

A

Iodine, chlorine

42
Q

What does iodine do?

A

Impair protein synthesis

Alter cell membrane by forming complexes

43
Q

What is an iodophore?

A

Iodine combined with organic molecule, less irritating

44
Q

Name an iodophore

A

Povidone-iodine

45
Q

What does chlorine form with water?

A

Oxidising agent hypochlorous acid (HOCl)

46
Q

How do alcohols work?

A

Denature proteins and lipids

47
Q

What do alcohols work against?

A

Bacteria and fungi

48
Q

What do alcohols not work against?

A

Endospores, non-enveloped viruses

49
Q

What heavy metals are used as microbial control?

A

Silver, mercury, copper

50
Q

How do heavy metals control microbial growth?

A

Combine with sulfhydryl groups (cysteine, methionie) denature proteins

51
Q

Where is silver used?

A

Dressing to treat infections with antibiotic-resistant bacteria

52
Q

Where is mercury used?

A

Paint to prevent mildew

53
Q

Where is copper used?

A

Reservoirs, ponds, swimming pools, fish tanks (its algicidal)

54
Q

How do aldehydes (formalin, glutaraldehyde) work?

A

Denature proteins through covalent cross linkning

55
Q

What are the 5 main sites antibiotics target?

A 
Cell wall synthesis
Protein synthesis
Nucleic acid replication/transcription
Plasma membrane
Essential metabolite synthesis
56
Q

Name a living antibiotic (not in use yet)

A

Bdellovibrio

Microbial world (12 decks)

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