sterilisation and disinfection

Question 1

what is sterilization?

Answer 1

sterilisation is a process by which all living microorganisms including viable spores are destroyed or removed from an article, surface or medium.

Question 2

what are sterilants?

Answer 2

agents which achieve sterilization.

Question 3

define disinfection

Answer 3

it refers to a process that removes most of not all pathogenic microorganisms but may or may not remove bacterial spores. they act on inanimate objects

Question 4

what are the types of disinfectants?

Answer 4

Disinfectants are categorised into 3 categories -

1) High level disinfectants - They are capable of killing bacterial spores and all other microorganisms

2) Intermediate level disinfectants- They are capable of killing all microorganisms but not bacterial spores

3) Low level disinfectants - They are capable of killing vegetative bacteria and enveloped virus, variable action on non enveloped virus and fungi.
No action on tubercle bacilli and spores

Question 5

what is cleaning?

Answer 5

it refers to reduction in the pathogenic microbial population to an extent where items can be used without a protective attire.

Question 6

methods of sterilization

Answer 6

physical methods -

1) heat based method ( >100 degree)
steam sterilizer ( autoclave)
dry heat sterilizer ( hot air oven)
filteration
radiation -
ionizing
non ionizing
others - incineration, microwave

chemical methods

plasma sterilizer
ethylene oxide sterilizer

Question 7

Steam sterilizer

Answer 7

principle - it works similar to a pressure cooker. follows law of gas

1) when vapour pressure equals atmospheric pressure water boils.

2) in a closed vessel as pressure rises, the boiling temperature also rises.

mechanism of action - Moist heat destroys microorganisms by coagulation, denaturation of enzymes and structural proteins.

uses -
1) In critical and semi critical devices which and heat and moist resistant. eg surgical instruments, dental instruments, surgical drapes and linens

2) culture media preparation

3) biomedical waste treament

Question 8

Types of sterilization

Answer 8

Horizontal type - Used in CSSD, large sized labs, biomedical waste treatment

vertical type - used in small labs

Question 9

Sterilization control

Answer 9

effectiveness of steam sterilizer can be observed by -

1) Biological indicators - spores of geobacillus stearothermophillus are killed at 121 degrees Celsius in 12 mins

chemical indicators -
1) External pack control
2) internal pack control
3) bowie - dick test

physical indicators - digital display of temp, time, pressure on equipment

Question 10

dry heat sterilizer