Lecture 9 and 10

Question 1

What was Louis Pasteur investigating when he discovered pasteurisation?

Answer 1

Fermentation (wine preservation)

Question 2

What did Pasteur discover among the yeast?

Answer 2

Bacteria

Question 3

What theories did Pasteur have?

Answer 3

Germ theory: cells germinate, cause spoilage

Germs could be killed by heat to prevent spoilage

Question 4

Who is the ‘father of antispetic surgery’?

Answer 4

Sir Joseph Lister

Question 5

What did Joseph Lister do?

Answer 5

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

Question 6

Who discovered penicillin?

Answer 6

Alexander Fleming

Question 7

What bacteria produces inhibitory substance penicillin?

Answer 7

Penicillium notatum

Question 8

How does penicillin kill?

Answer 8

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

Question 9

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

Answer 9

Sir Ernst Chain

Lord Howard Florey

Question 10

Define sterilisation

Answer 10

Removal of all forms of microbial life

Question 11

How are things sterilised?

Answer 11

Pressured steam/gas

Question 12

What is commercial sterilisation?

Answer 12

Sufficient heat to kill Clostridium botulinum endospores in canned food

Question 13

What is disinfection?

Answer 13

Destruction of vegetative pathogens on inaminante objects

Question 14

What is antisepsis?

Answer 14

Destruction of vegetative pathogens on living tissue

Question 15

What is degerming?

Answer 15

Removal of microbes from a limited area

Question 16

What is sanitisation?

Answer 16

Lowering microbial counts on eating/drinking utensils

Question 17

What is biocide/germicide?

Answer 17

Kills microorganisms

Question 18

What is bacteriostasis?

Answer 18

Inhibition of growth/multiplication of bacteria

Question 19

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

Answer 19

Decimal reduction time

Question 20

What are three methods of action of microbial control agents?

Answer 20

• Alteration of membrane permability
• Damage to proteins
• Damage to nucleic acids

Question 21

Give an example of damaging nucleic acids.

Answer 21

UV causes thymine dimers to form

Question 22

What is the main type of bacteria that produces endospores?

Answer 22

Gram positive bacteria living in the soil

Question 23

Why do soil bacteria produce endospores?

Answer 23

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

Question 24

How can microbial control agents be evaluated?

Answer 24

Use- dilution test

Disk diffusion method

Question 25

How is the use-dilution test carried out?

Answer 25

``` 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 ```

Question 26

What is disk diffusion method?

Answer 26

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

Question 27

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

Answer 27

Thermal death point

Question 28

What is thermal death time?

Answer 28

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

Question 29

What is decimal reduction time?

Answer 29

Time required to kill 90% of the micoorganisms

Question 30

What is the temperature used in an autoclave?

Answer 30

121C

Question 31

What is the pressure in an autoclave?

Answer 31

15psi

Question 32

How long is an autoclave run for?

Answer 32

15min for 10ml volume

Question 33

What can't an autoclave kill?

Answer 33

Prions

Question 34

What temperature and time is required for pasteurisation?

Answer 34

72C for 15 seconds

Question 35

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

Answer 35

140C for 4 seconds

Question 36

What are phenolics?

Answer 36

Derivative of phenol, less irritating

Question 37

How do phenolics work?

Answer 37

Destroy lipids in cytplasmic membrane

Question 38

How does triclosan (a phenolic) work?

Answer 38

In soaps/toothpaste etc. | Inhibits enzyme for lipid biosynthesis

Question 39

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

Answer 39

Biguanides (chlorhexidine)

Question 40

What does chlorhexidine not work against?

Answer 40

Psyedomonads (Gram negative) | Endospores

Question 41

What halogens are used to control microbial growth?

Answer 41

Iodine, chlorine

Question 42

What does iodine do?

Answer 42

Impair protein synthesis | Alter cell membrane by forming complexes

Question 43

What is an iodophore?

Answer 43

Iodine combined with organic molecule, less irritating

Question 44

Name an iodophore

Answer 44

Povidone-iodine

Question 45

What does chlorine form with water?

Answer 45

Oxidising agent hypochlorous acid (HOCl)

Question 46

How do alcohols work?

Answer 46

Denature proteins and lipids

Question 47

What do alcohols work against?

Answer 47

Bacteria and fungi

Question 48

What do alcohols not work against?

Answer 48

Endospores, non-enveloped viruses

Question 49

What heavy metals are used as microbial control?

Answer 49

Silver, mercury, copper

Question 50

How do heavy metals control microbial growth?

Answer 50

Combine with sulfhydryl groups (cysteine, methionie) denature proteins

Question 51

Where is silver used?

Answer 51

Dressing to treat infections with antibiotic-resistant bacteria

Question 52

Where is mercury used?

Answer 52

Paint to prevent mildew

Question 53

Where is copper used?

Answer 53

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

Question 54

How do aldehydes (formalin, glutaraldehyde) work?

Answer 54

Denature proteins through covalent cross linkning

Question 55

What are the 5 main sites antibiotics target?

Answer 55

``` Cell wall synthesis Protein synthesis Nucleic acid replication/transcription Plasma membrane Essential metabolite synthesis ```

Question 56

Name a living antibiotic (not in use yet)

Answer 56

Bdellovibrio