Topic 6 - Microbial control

Question 1

Why it important to have microbial control?

Answer 1

• Prevent culture contamination - Prevent equipment contamination - Increase shelf life

Question 2

What is: Sterilization Disinfection Antisepsis Degermining Commercial sterilization Sanitization

Answer 2

Sterilization- killing/removal of all microbes Disinfection - Removing pathogens Antisepsis - Removing pathogens from living tissue Degerming - removing microbes from limited area Sanitization - lowering microbial counts Commercial sterilization - killing C.botulinum endospores which stops growth and no pathogen left

Question 3

What is: biocide/germocide Bacteriostasis sepsis asepsis

Answer 3

Biocide/germocide - kills microbes bacterostais - inhibiting microbes (not killing) Sepsis - microbial contamination Asepsis - absense of significant contamination

Question 4

What determines the level of effectiveness of treatments?

Answer 4

• Time of exposure - Number of microbes - Environments if they are on organic matter, have biofilms and the temperature - Microbial characteristics

Question 5

What do microbial control agents do?

Answer 5

• Alter membrane permeability - Denature proteins - Damage nucleic acids

Question 6

What are some physical control mechanisms?

Answer 6

• Desiccation - Osmotic pressure - Temperature - Moisture - Pressure - Radiation - Filtration

Question 7

How does heat affect microbes?

Answer 7

It denatures their proteins,

Question 8

What is TDP?

Answer 8

Thermal death temperature. It is the lowest temperature that kills ALL cells in 10 mins.

Question 9

What is TDT?

Answer 9

Thermal death time. It is time during which all cells are killed.

Question 10

What is DRT?

Answer 10

Decimal reduction time. This is the time that kills 90% of population at given temperature.

Question 11

Answer 11

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Question 12

What is autoclaving?

Answer 12

It is sterilization but using steam. It kills everything but prions.

Question 13

What does sterilization time using the autoclave depend on?

Answer 13

Sterilization time depends on volume, e.g. 10 mls = 15mins

6L - 70 mins

Question 14

Answer 14

It uses steam as opposed to water, it has higher temperatures them boiling and higher pressure.

Question 15

What is an important apparatus for steam sterilization?

Answer 15

The sterilization strip which confirms sterilization.

Question 16

What are the properties of dry heat sterilization?

Answer 16

• Kills by oxidation
• incineration
• flaming
• hot air sterilization.

Question 17

What is the equivlance of dry heat to autoclaving?

Answer 17

autoclaving requires less temperature and less time.

Question 18

What does pateurization do?

Answer 18

It reduces spoilage organisms.

Question 19

What does pastuerization consists of?

Answer 19

High temperatures for 15 sec - 72 degrees

Ultrahigh temperatures for < 1 sec - 120 degrees

Question 20

What does refrigeration do?

Answer 20

It slows down metabolism and is usually bacteriostatic.

Question 21

What does freezing do?

Answer 21

Forms ice crystals which affect cells. Slow freezing is more affective than flash freezing.

Question 22

What is freeze drying and what does it do?

Answer 22

Freeze drying helps preservation and it reduces the amount of water present.

Question 23

What are the different types of filtration and what are the properties?

Answer 23

There is HEPA filtration which filtrates >0.3 µm and there is membrane filtration which removes 0.22µm.

Question 24

Filtration doesnt…..?

Answer 24

• Inactivate any metabolic activity (toxins)
• Work on viruses

Question 25

Answer 25

1. Removal of moisture
2. Pressure exerted which prevents osmosis when seperated by pure solvent.
3. Atmospheric condition where pressure his above average.
4. Emission of energy as electromagnetc waves which causes ionization.

Question 26

What is the disc diffusion method?

Answer 26

• Add the microbe, just smear it along the entire plate.
• Add the antibiotic disc.
• Incubate which allows for bacterial growth and disc to diffuse.

Question 27

What do phenols, bisphenols and phenolics do?

Answer 27

They all disrupt the cell membrane.

Question 28

What are exmaples of bisphenols?

Answer 28

• hexacholophene and triclosan.

Question 29

What do biguanides do? What are they used for?

Answer 29

They stop lipid absorption through the cell membrane, e.g. chlorohexidine.

They are used for - antiseptic, disinfection and perservation.

Question 30

What are these used for..?

Answer 30

Question 31

What are quats effective against?

Answer 31

Bacteria, viruses, fungi and amoebae (Benzalkonium chloride and Cetylpyridinium chloride). They do not kill enodpores or mycobacteria.

Question 32

Answer 32

Physical and chemical barriers affect how resistant microbes are.

Question 33

What is aseptic technique?

Answer 33

It is a procedure and practice that aims to minimise unwanted microbial contamination.

Question 34

What are some examples of aseptic technique use?

Answer 34

• Culturing microbes
• Cell culture
• Surgery
• Wound care

Question 35

What did Ehrlich discover?

Answer 35

That different organisms have different types of cells and therefore need unique drugs to target those cells.

Question 36

What is an example of “magic bullet’? Who discovered it?

Answer 36

Penicilin and it was dsicvered by Fleming.

Question 37

Answer 37

Broad spectrum - Active against both gram-negative and gram-positive bacteria, tetracyclines, phenicols etc.

Narrow - have limited activtiy and are usually used agaisnt a particular species, glycopeptides and bacitracin for gram positive and polymixins are agaisnt gram negative.

Question 38

What are antibiotic modes of action?

Answer 38

Question 39

Answer 39

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