Growth limitation and sterilisation techniques

Question 1

For how long should items be autoclaved at 121°C?

Answer 1

15 minutes

Question 2

What are Browne’s tubes?

Answer 2

Used to show that sterilisation has taken place during autoclaving.

Question 3

For how long should items be autoclaved at 126°C.

Answer 3

10 minutes

Question 4

Examples of objects that CAN be autoclaved

Answer 4

Culture media, scalpels and glassware such as test tubes and conical flasks.

Question 5

Examples of items that should NOT be autoclaved…

Answer 5

Items that may be adversely affected by steam, such as powders, oils, glass pipettes and metal instruments that may corrode if exposed to moisture. Also media with heat-sensitive components such as proteins.

Question 6

Sterilisation

Answer 6

a process that kills all micro-organisms, including endospores, within a material or object

Question 7

Autoclaving

Answer 7

Technique that uses pressurised steam to kill microorganisms

Question 8

Biostatic disinfectant

Answer 8

Prevents bacteria from reproducing

Question 9

Bacteriocidal disinfectant

Answer 9

Kills bacteria

Question 10

Factors affecting the effectiveness of disinfectants are

Answer 10

the concentration and the time applied

Question 11

Sterilisation using dry heat at 160 degrees centrigrade would take how long?

Answer 11

2 hours

Question 12

Disinfectant

Answer 12

Used to kill microorganisms, but cannot achieve sterility

Question 13

Steps to clean up small scale spillages

Answer 13

1. Put on gloves
2. Cover spillage with paper towels
3. Pour disinfectant around and over spillage
4. Leave on for 10 minutes
5. Sweep debris into dustpan
6. Autoclave debris

Question 14

Spores/endospores

Answer 14

Dormant structure formed from a bacterial cell that can survive extremely adverse conditions such as high temperatures.

Question 15

Gamma irradiation

Answer 15

Gamma rays are used to sterilise items such as plastics, syringes and surgical gloves.

Question 16

Filtration

Answer 16

Method of sterilising liquids, liquid passes through but microorganisms are trapped and removed.

Question 17

Hazard

Answer 17

the danger or harm that may be caused (e.g. by a microorganism).

Question 18

Risk

Answer 18

The likelihood of harm

Question 19

Simple risk assessments

Answer 19

involve the use of micro-organisms and procedures that pose a familiar hazard and well-known control measures

Question 20

Generic risk assessments

Answer 20

involve the use of an authoritative source of advice or code of practice for the safe handling of a micro-organism when using a particular procedure.

Question 21

Novel risk assessment

Answer 21

is the procedure adopted for an unfamiliar hazard that is not covered by the generic code of practice. In this case, you must research the potential risks from first principles.

Question 22

Methods to contain large scale spillages

Answer 22

drains do not directly lead to the main sewerage system. Floors and walls are sealed. Doorways are positioned above ground level.

Question 23

Control measure - PPE

Answer 23

Personal protective equipment: A laboratory coat worn correctly protects your everyday clothes from contamination. Eye protection. Gloves can be worn to protect hands. Cuts should be covered with waterproof plasters.

Question 24

Control measure - choice of organism

Answer 24

Select one with the fewest hazards, from a reputable source. Use correct storage and labeling and log books.

Question 25

Control measure - media selection

Answer 25

Use selective media where possible

Question 26

Control measure - culture methods

Answer 26

Select correct conditions, don’t promote the growth of anaerobic bacteria, use plastic rather than glass.

Question 27

Control measure - handling procedures

Answer 27

Prevent aerosol formation. Introduce loops gradually into the Bunsen flame. Take care when opening containers of micro-organisms. Consider the scale of the operation, degree of containment and likelihood of contamination.