Control of Microbial Growth Flashcards
What is sterilisation?
3
Complete destruction or elimination of all viable organisms
Killing or removal of all viable organisms
Includes the destruction of endospores
Through what two ways is the growth of microbes affected?
By killing microorganisms
By inhibiting the growth of microorganisms
What are the three ways to prevent microbial transmission?
Standard precautions e.g. hand hygiene
Transmission-based precautions
Surveillance - investigating and monitoring IPC practice
What are the two main types of agents used to control microbial growth?
Physical agents
Chemical agents
Give three examples of physical agents used to control microbial growth.
Heat
Radiation
Physical removal of cells
Give an example of a chemical agent used to control microbial growth.
Antimicrobials
What do antimicrobials do?
They kill or inhibit microbial growth
Give two examples of antimicrobials.
Disinfectants
Antibiotics
Where are disinfectants used?
In the environment
Where are antibiotics used?
In the human host
What are the three measures used to control growth in the environment.
Decontamination
Disinfection
Sterilization
What is decontamination?
Treatment that renders an object or inanimate surface safe for use or disposal
What is disinfection?
2
Destruction of vegetative organisms which might cause disease
Does not necessarily kill spores
What is considered the ultimate means of controlling microbial growth?
Sterilization
What are the two ways to control microbial growth in humans?
Antibiotics
Vaccines
What four methods of sterilization are used in the lab?
Red heat
Dry heat
Moist heat
Filtration - heat sensitive materials
What are the three methods of sterilisation in the Healthcare environments?
Moist heat
Radiation
Incineration
When is incineration carried out in a Healthcare environments?
It is used for the disposal of medical waste
When is radiation used in a Healthcare environment?
Used for drugs, tissue grafts and medical supplies
When is moist heat used in a Healthcare environment?
Autoclaving
Used for medical devices
What are the four most commonly used different methods of heat sterilization?
Red heat
Dry heat
Autoclaving
Incineration
Why should moist heat be used instead of dry heat where possible?
(2)
Moist heat has more penetrating power than dry heat
Moist heat produces a faster reduction in the number of living organisms
What temperature is needed to kill endospores?
121 degrees for 5 minutes
Why must temperatures reach 121 degrees for five minutes during heat sterilization?
As endospores are more thermoduric than vegetative cells
What are the three time periods involved in heat sterilization?
Heating-up period
Holding period
Cooling down period
What is the heating-up period?
The time needed for the entire load to reach sterilizing temperature
What is the holding period?
The time for sterilization to occur
What is the cooling down perios?
The time for the load to cool down
Where is the only place where red heat is used in sterilization?
In micro labs
Where is dry heat sterilization primarily used?
In the micro lab
What is used to perform dry heat sterilization?
A hot air oven
What is a hot air oven?
2
A thermostatically controlled oven
Fitted with a fan to ensure even temperature
Can dry heat be used to sterilize?
No
Why can’t dry heat be used to sterilize?
3
Sterilization time is too high
Higher temperatures are needed (160-170)
Too long and high for media
What is dry heat used for?
3
Glassware
Metal
Objects that won’t melt
Why is an autoclave used in the microbiology lab?
6
Sterilize culture media
Sterilize reagents
Sterilize equipment before use
Safe discard biohazardous wate
Safe discard of specimens
Safe discard of agar plate
What exactly is autoclaving?
Steam under pressure at temperatures above the boiling point of water
List some of the different types of autoclaves.
2
‘Pressure cooker autoclave’
Gravity displacement autoclave
What is a pressure cooker autoclave?
2
A metal chamber with a strong metal lid
An air/steam discharge tap
What is a gravity displacement autoclave?
4
Outer jacket filled with steam under pressure
Inner chamber - steam enters this chamber and forces the air out be gravity displacement
A thermocouple probe is inserted inside the chamber and around the load to monitor the load temperature
Interlocking devices prevent the opening of the door until temperature of load has fallen
Where are gravity displacement autoclaves used?
2
Diagnostic labs
Healthcare CSSD
What needs to be remembered when using an autoclave?
3
Materials must be packaged loosely
Sterilisation wrap or autoclave bags must be used to allow steam penetration
Autoclave indicator tape must be applied
How does autoclave tape work?
2
Tape has diagonal markings made with temperature sensitive ink
Black stripes will become visible when the correct temperature is reached
What is incineration used for?
The safe disposal of hazardous and high risk clinical waste
What is filter sterilisation?
The physical removal of microorganisms from the air or liquids (does not trap viruses)
When are membrane filters used?
For sterilization of heat-sensitive liquids e.g. antibiotic solutions
How are membrane filter used?
Solutions are passed through a filter of sufficient pore diameter to remove the smallest known bacterial cells
What type of radiation is most used in sterilisation?
Electromagnetic radiation
Name the two different types of electromagnetic radiation used in sterilization.
Ultraviolet radiation
Ionizing radiation
How does UV radiation work?
UV lamps cause the break in DNA
Where is UV radiation used?
Used for workspaces and tools used in microbiology labs and healthcare facilities
What are the disadvantages of UV radiation?
2
It only decontaminates surfaces
Microbes can be shielded from UV in fissures, cracks and shaded areas
What are the benefits of ionizing radiation?
Gamma rays are highly effective in killing microorganisms and do not have sufficient energy to impart radioactivity
How does ionizing radiation work?
Gamma rays degrade DNA and protein
When is ionizing radiation used?
Widely used for sterilization in Healthcare facilities
What are disinfectants?
Chemicals used to kill microbes but not necessarily their endospores on inanimate objects or surfaces
Where are disinfectants used?
4
Microbiology lab
Hospital environments
Food industry
Drinking water
Why are disinfectants used in the microbiology lab?
For safe discard and to decontaminate surfaces
Why are disinfectants used in the hospital environment?
To decontaminate surfaces and heat sensitive materials
Why are disinfectants used in food industry?
To reduce microbial load and make surfaces safe to handle
What are the seven limitations of disinfectants?
7
Susceptibility of microorganisms to disinfectants varies
Endospores are generally resistant
Inactivated by clinical materials such as blood and plastics
Activity is reduced in the presence of large numbers or microorganisms such as biofilms
Must be made fresh daily
Must be made up at the correct concentration
May be sensitising and corrosive to skin
Name three common disinfectants.
Virkon
TriGene
Hypochlorite
How does hypochlorite work?
2
Activity due to chlorine
Very effective against, viruses and endospores
