Control Of microbial growth

Question 1

Define Themal death point

Answer 1

The lowest temperatre required to kill all organisms

Question 2

Define thermal death time

Answer 2

The amount of time required to kill all organisms at a given temperatre

Question 3

What are the 2 types of autoclaving

Answer 3

Gravity displacement or pre-vaccum

Question 4

What is pasturisation

Answer 4

Killing of pathogens and reducing the spoilage oforganisms

Question 5

What are the 3 types of pasturisation

Answer 5

HTST, UHTS

Question 6

What are the conditions of HTST pasturisation

Question 7

What are the conditions of UHT pasturisation

Question 8

How does ionising radiation sterlise surgical equipment

Answer 8

By breaking double stranded dna (most commonly used is gamma or x-rays

Question 9

What is sonification and how does to work to stertise

Answer 9

High frequency ultrasound waves, causes a rapid change in pressure. This is used to call cell lysis

Question 10

What does oligodynamic mean

Answer 10

Active at small concentrations

Question 11

What does desiccation mean

Answer 11

Reduction of water activity

Question 12

What is ionising radiation used to sterilise

Answer 12

Heat sensitive and packaged material

Question 13

What is non ionising radiation good for sterilising

Answer 13

Surfaces

Question 14

What is the risk of using heavy metals as disinfectants

Answer 14

Their toxicity and the environmental risks

Question 15

Where is chlorine typically used as a disinfectant

Answer 15

In water bodies such as swimming baths

Question 16

What are the positives of using phenolics

Answer 16

They’re stable and long lasting

Question 17

Where are HEPA filters typically used

Answer 17

In hospital ventilation systems it in labs

Question 18

What are the positives and negatives of using alkylating agents to sterilise materials

Answer 18

They can effectively sterilise at low temperatures, but they’re carcinogenic

Question 19

What factors can effect the effectiveness of disinfectants

Question 20

What is disk diffusion used to check

Answer 20

Used to test efficacy against a particular microbe

Question 21

What is use dilution used to check

Answer 21

To test efficacy on a surface

Question 22

Why is moist heat more effective

Answer 22

Because it’s better able to penetrate the plastic packaging of instruments and is more effective at penetrating cell membranes

Question 24

What is the disk diffusion method

Answer 24

Application of chemicals to filter paper, then placing them on agar, when the bacteria grows zones of inhibition will grow

Question 25

What does the zones of inhibition show about the chemical and the bacteria

Answer 25

The larger the zone the more effective the chemical is at killing the bacteria.

Question 26

How is the zone of inhibition measured

Answer 26

By calculating the area by measuring the diameter

Question 27

What is the use dilution test

Answer 27

Penicylinders are soaked and dried in bacteria, are treated with disinfectant. They’re then placed into a growth media for 48 hours to determine if any have survived

Question 28

What are the strengths of the use dilution test

Answer 28

Is a high level test for disinfectants. Is an approved method by the environmental protection agency

Question 29

What are the weaknesses of use dilution tests

Answer 29

They’re subject to variability. They’re far removed from the real life use of disinfectants

Question 30

What is the method for the in use test

Answer 30

1ml of disinfectant is mixed with 9ml of sterile broth ( with disinfectant inhibitor). Then place 10 drops onto each of the 2 agars. Incubating one at 37•c for 3 days and the other at room temp for 7 days

Question 31

What do the results of an in use test show

Answer 31

If 5+ colonies are viewed then contamination has occurred

Question 32

What is the phenol coefficient method

Answer 32

Tests the potency of a disinfectant compared with phenol. A series dilution is made and then test bacteria are added and incubated at 37•c. Samples are taken at 5 minute intervals If the value if larger than 1 then it implies better activity than phenol

Question 33

What are the disadvantages of the phenol coefficient method

Answer 33

It can lead to misleading results

Question 34

What is the number of common methods used to test potency of a disinfectant

Answer 34

Four

Question 35

What type of heat do auto claves use

Answer 35

Moist

Question 36

What’s another term for dessication

Answer 36

Drying

Question 37

What happened to the boiling point of water at higher altitudes

Question 38

What two things are used in high concentration in dessication

Answer 38

Salt and sugar

Question 39

Which heavy metal is historically known to treat syphilis

Answer 39

Mercury

Question 40

Which heavy metal causes argyria

Answer 40

Silver

Question 41

What types of compounds facilitate the slow release of chlorine

Answer 41

Chloromines

Question 42

What type of dimmers are caused by non ionising radiation

Answer 42

Thymine

Question 43

What’s the type of compound where iodine is complexed with an organic molecule

Answer 43

Iodofour

Question 44

In an auto clave what is air replaced by

Answer 44

Stream

Question 45

What is the term used to denote complete removal or killing

Answer 45

Sterilisation

Question 46

Beta- propionolactone is quickly metabolised into

Answer 46

Lactic acid