Microbial Control (W3)

Question 1

what are the 4 controls of microbial growth

Answer 1

1. cleaning
2. sanitisation
3. disinfection
4. sterilisation

Question 2

what is achieved by disinfection

Answer 2

removal of pathogens only

Question 3

what is achieved by sterilisation

Answer 3

removal of all microbes, including bacterial spores

Question 4

what is achieved by cleaning

Answer 4

removal of visible soils and microorganisms are removed but not killed

Question 5

what is achieved by sanitisation

Answer 5

destroys enough microorganisms to meet safety guidelines, not effective in presense of organic matter

Question 6

define germicide

Answer 6

an agent that kills pathogenic organisms

Question 7

what are the 2 types of germicide disinfection and what are they both used for

Answer 7

Disinfectant- inanimate objects

Antiseptic - animate areas

Question 8

what are 4 methods of disinfection

Answer 8

• pasteurisation
• radiation
• heat (boiling)
• Chemical solutions

Question 9

describe pasteurisation generally

Answer 9

• takes place at 60 - 80 deg for a few mins
• kills pathogens and most other bacteria
• it reduces spoilage bacteria
• Extends shelf life

Question 10

what are the 2 ways pasteurisation can be conducted and their conditions

Answer 10

1. Low Temp + Long Time = 63 deg for 30 mins
2. High Temp Short Time = 72 deg for 15 secs

Question 11

what 3 radiations can be used for disinfection

Answer 11

• ultra-violet
• non ionising radiation
• ionising radiation (electron beam, gamma rays and X rays

Question 12

how does ultraviolet radiation kill bacteria and how is it used

Answer 12

• it kills bacteria by damaging proteins and nucleic acid
• it has a low penetration power, and is used for a moderate exposure time (3 hours)

Question 13

what are the 3 modes of action of chemical disinfection and give an example of each

Answer 13

1. protein coagulation and denaturation
   eg. Alcohols and aldehydes
2. disruption of cell membrane
   eg. Surface Active Antigens
3. inactivation of enzymes ( chemical antagonism )
   eg. Metals

Question 14

How (3) does organic matter inhibit disinfection

Answer 14

1. Forms a precipitate
2. reacts to produce non-bactericidal agents
3. Coats bacteria

Question 15

why are endospores difficult to kill

Answer 15

they are covered in thick spore coat that protects from chemicals and radiation

Question 16

Why is moist heat better than dry heat?

Answer 16

moist heat is better because moisture is a good conductor of heat, therefore it has better heat penetration

Question 17

What are the typical conditions used for moist heat sterilisation?

Answer 17

15 mins at 121deg and 15 psi

Question 18

when would you use a dry heat oven instead of autoclaving

Answer 18

dry heat is used for oils, powders, sharp objects and glassware

Question 19

what are the 3 methods we can use to ensure the autoclave is working properly

Answer 19

• autoclave printout
• Bowie-dick tape
• spore strips

Question 20

how does ionising radiation kill microbes

Answer 20

by disrupting chemical bonds that damages DNA

Question 21

what are 2 chemicals used for cold sterilisation

Answer 21

• formaldehyde
• ethylene oxide

Question 22

what filtration pore size is needed to filter out bacteria and what size for viruses

Answer 22

bacteria = 0.45um
viruses = 0.01um (or 10nm)

Question 23

what is a bacteriostatic agent and what is a bactericidal agent

Answer 23

bacteriostatic prevent reproduction
bactericidal kill cell (by damaging cell wall)

Question 24

what are the 6 modes of action for antibacterial agents

Answer 24

1. cell wall synthesis inhibitors
2. inhibit DNA replication
3. inhibit RNA synthesis
4. inhibit ribosome function / protein synthesis
5. metabolic inhibitors
6. membrane active antimicrobial agents

Question 25

how does B-lactam work as an antibiotic

Answer 25

B lactam disrupts the final stage in cell wall synthesis

Question 26

How does not finishing an antibiotic treatment lead to bacterial resistance

Answer 26

bacteria are exposed to the antibiotic but are not killed so they are able to reproduce and potentially develop resistance

Question 27

Define the Antibiotic Creed

Answer 27

the antibiotic creed is a guideline on how/when to prescribe/take antibiotics

Question 28

what does MINDME stand for

Answer 28

M - microbiology guides therapy wherever possible I - indications should be evidence based N - Narrowest spectrum required D - Dosage appropriate to size and type of infection M - minimise duration of therapy E - ensure monotherapy in most cases